Why are Inverted Colors considered an accessibility feature?

Question

Why is it that, in most operating systems, the "Inverted Colors" display setting is considered an accessibility feature? Both Windows and OS X include this option so it seems to be a recognized feature and not a vendor-specific quirk.

I understand that some users are color-blind. This could possibly justify the Black & White, or grey-scale modes for developers wanting to be assured that the experience is cohesive for everyone. What I don't understand is how or why does inverting the display color help someone with any specific, visual impairment or dysfunction.

As a programmer that wants to understand the need so that I can develop better accessible software, what purpose does this feature serve to the end user who has some form of visual impairment?

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UPDATE

I asked this question quite a while ago, however, it just dawned on me -- I think I am one of those individuals that this feature was designed for. I almost always try to keep the contrast reversed from the typical settings for my text displays. I hate white backgrounds with dark text! As a coder, all of my textual GUIs are black with green text. This isn't just a throwback to the old monochrome, green screen days. The pairing of the two colors is quite comfortable to my eyes. However, staring at too much black-on-white actually hurts my eyes from some form of eye strain.

I mention this in an update because the color inversion feature is not useful.. it's annoying! As someone who needs a good feature like this, it's a shame that all implementations that I have ever seen are just a poor attempt at solving a problem. I would hope that Apple, Microsoft and others have done their research but I'm guessing that might not be the case. Color inversion just feels like slapping a band-aid on a bigger problem.

Developers, if you want to help people who need such a feature as to prevent eye-strain, find ways to change the text and page background and not necessarily the entire display.

Answer 1

Research generally suggests light on dark is harder to read in most cases but considering we're talking accessibility, you should know that results for those with normal vision don't necessarily hold true for those with various vision impairments.

I've heard higher contrast (the mode in Windows is called High Contrast mode I think) can be easier to read for those with impaired vision though; the white text seems to stand out more. I'm curious as to why that is psychologically; the actual contrast ratio should technically be the same between white on black vs black on white.

Note that it's recommended to increase font sizes and leading when inverting text colors:

When reversing colour out, eg white text on black, make sure you increase the leading, tracking and decrease your font-weight. This applies to all widths of Measure. White text on a black background is a higher contrast to the opposite, so the letterforms need to be wider apart, lighter in weight and have more space between the lines.

Mark Boulton

Also, a common reason for white on black (which this feature mostly produces) is for night reading; many e-readers offer a Night Mode with white on black. The black screen is less painful to read with low to no external light.

Another reason it might be common is simply because it's easy and relatively safe to to implement. Compare it to other obvious color effect options; if you tried to Sepia tone the whole screen (an effect I've seen to make reading easier on the eyes) you would reduce contrast significantly. Turning things black and white could eliminate color cues used to differentiate interface elements.

Simply inverting colors preserves the relative contrast between UI elements (so you won't have black text on grey backgrounds), so it's a "safe" effect at the least. And if it doesn't help, no harm done, just undo the effect.

Answer 2

True color blindness, where someone cannot distinguish colors at all, is extremely rare. A far more common condition, which affects up to 10% of the male population, is red-green weakness. People suffering from it cannot easily distinguish red and green, and some hues may seem completely identical to them.

While there is no guarantee (there are different kinds and grades of red-green weakness), there is a good chance that UI elements a red-green weak person cannot see well will become more distinguishable when the colors are inverted.

Answer 3

The color:invert property is really just about increasing the contrast ratio of the text. It selects the inverse color of the background color. Contrast is the key to increasing the accessibility of the text.

There is a load of information on this over at W3.org

• To pass AA compliance you need a contrast-ratio of 4.5:1.
• To pass AAA compliance you need a contrast-ratio of 7:1

A contrast ratio of 3:1 is the minimum level recommended by [ISO-9241-3] and [ANSI-HFES-100-1988] for standard text and vision. The 4.5:1 ratio is used in this provision to account for the loss in contrast that results from moderately low visual acuity, congenital or acquired color deficiencies, or the loss of contrast sensitivity that typically accompanies aging.

...

Hues are perceived differently by users with color vision deficiencies (both congenital and acquired) resulting in different colors and relative luminance contrasts than for normally sighted users. Because of this, effective contrast and readability are different for this population. However, color deficiencies are so diverse that prescribing effective general use color pairs (for contrast) based on quantitative data is not feasible. Requiring good luminance contrast accommodates this by requiring contrast that is independent of color perception. Fortunately, most of the luminance contribution is from the mid and long wave receptors which largely overlap in their spectral responses. The result is that effective luminance contrast can generally be computed without regard to specific color deficiency, except for the use of predominantly long wavelength colors against darker colors (generally appearing black) for those who have protanopia. (We provide an advisory technique on avoiding red on black for that reason)

It's all slightly different when you start using text of +18pt though, but there is plenty of guidence out there around this. The great snook colour contrast checker is a useful site that allows you to input hex color values to see whether they pass the various W3C criteria.

Answer 4

Some more background on this feature: in Windows, the feature commonly called High Contrast mode is perhaps best thought of as "Use the user's preferred colors mode". In this mode, apps are supposed to use whichever colors the user has selected for text, background, window border, and other screen elements via the control panel.

This mode was completely customizable, and could be used with any of the preset color schemes (such as high contrast black-on-white or high contrast white-on-black, both of which had distinct colors for text elements vs background elements to ensure good contrast), or a user-defined theme. However, since the default color scheme when using the keyboard shortcut to activate this mode was the white-on-black scheme, the mode became associated with that color scheme - which looks very similar to inverse video - even though that's not it's specific goal.

While this feature was originally very flexible, it has one major problem in that it relies on all apps to implement support for it correctly in order for it to work consistently. Apps have to check whether the mode is enabled or not, and if enabled, obtain the system colors to use instead of their own theme or skin colors. What you typically find is that apps from Microsoft and other major vendors who are aware of this mode will actually do this work, but many smaller 3rd party apps will ignore the mode outright, as the developers may not be aware of the feature in the first place. This can lead to situations where some apps get 'inverted', others remain as-is, and some end up as a messy hybrid of inverted and non-inverted controls.

(Some apps even go a step or two further: if this flag is set, IE will stop displaying background images - this was back when background images were typically used just for displaying textured backgrounds which could interfere with reading the text on top, as in the days of Myspace. Later on, however, background images ended up being used for meaningful content - ie sprites and image replacement - so pages that use those techniques don't work so well in IE when this mode is enabled!)

To avoid many of these issues, other vendors (RIM, Apple, others) take a completely different approach: instead of having settings that every app must carefully check for and respect, they simply let apps draw as usual, and then invert the final screen image as it is going to the physical display. As far as the apps are concerned, the screen is still in 'normal' colors, it's only the user that sees the inverted (or gray scale, depending on settings) image. The feature lives entirely in the OS, no app support needed.

It's worth noting that systems that use this approach end up affecting everything on the screen: text and background are inverted, but so are colors in images and video, which may provide no benefit to the end-user and may instead render the image/video unusable!

Also of note is that "inverse video" is not high contrast; in fact, contrast is (mostly) preserved: low-contrast light-grey-on-white gets transformed to equally low-contrast dark-grey-on-black.

So, long story short: 'inverse video' mode is something of a compromise feature: the original "Use the user's preferred colors (which may or may not be contrasting colors) mode" mode is far more flexible and accessible in theory, but not well supported. Inverse video is less useful, but can be supported 100%.

Answer 5

Using a white background is like staring at a lamp all day.

I've never understood the confusion people have about using dark backgrounds and lighter text. The only reason we ever used light backgrounds is because historically paper had to be light to show up dark inks. (But that practice is not ancient or severe enough to affect our evolution, so it is not more natural to us.) However, one additional feature I would welcome would be textured backgrounds. I think breaking up the surroundings of text is also easier on the eyes and may be more natural than bold detail of defined text.

Answer 6

I have visual impairment its more hard for me reading something with a dark color in a light background than something with a light color in a black background for me color inversion is really helpful the best color inversion that i seen in a OS was iOS color inversion and the worst was the Android color inversion in general Androids accessibility is really bad

i have to say that a native dark themealways is better than color inversion only problem is that too few developers are interested in put a dak skin in their applications right now i remember Sonys walkman music player

Answer 7

In some point inverting colors is helpful. For me, working in the office with computers around all day long my eye could strain a lot because of the brightness of the display. such microsoft word excel, etc.

I prefer inverting colors when typing. When I finish typing I revert it back.

I prefer to invert color because it is less bright on the text not the entire background. Less brightness on the display less effect on the eyes and the skin (radiation) . that's the reason why apple add invert colors to sooth your eyes especially for those who are sensitive in brightness

Answer 8

I am one of those people. As monitor size grown it went from unnoticed to a preference to a necessity. It burns my eyes if I look at a white screen too long.

If you think about it, you realize that it is essentially staring into a light-bulb. It baffles me how we could think that was a good idea. Or maybe it wasn't well thought out. White initially looks more attractive.

Answer 9

There is a partial explanation here:

http://webaim.org/articles/visual/lowvision#highcontrast

WebAim's recommendation is to allow the user to choose foreground and background.

One of the reasons why some people prefer black background and white or orange text is to minimise eye strain, especially if you are looking at the screen for a long time, e.g. white backgrounds can be too bright for some people, as suggested here:

http://www.wikihow.com/Reduce-Computer-Eye-Strain-by-Switching-to-High-Contrast-(Windows-7)

Answer 10

I'm a partially blind undergrad. Accessibility: The black background causes less eye fatigue than a typical white. Additionally, ads, photos, etc. are typically designed to visually POP and be seen and processed whether the reader is focused on them or not. Taking these images out of their native color scheme reduces that tremendously.

Meanwhile, I genuinely see yellow text on black background better. I don't know if this is psychological in that the constant pairing of this color scheme with other accessibility features has trained me to be more receptive, or if it's physiological.

However, the preinstalled inversion setting is like a crutch while you wait for an artificial leg. There are much better options out there.

Answer 11

For people with bad eye floaters the colour inversion is very helpful since there is less bright light to create the shadows caused by the eye floaters.

Answer 12

Invert Colors in iOS devices is to make the digital screen comfortable to look at and ease the eyestrain.

The usage of Invert Colors in iOS is the same as F.lux in Windows/Mac computer, Twilight (a free app) in Android phone.

Since Apple has lots of limits for approving an app in iTunes Store, there is not F.lux-like app for iOS devices to reduce eye strain and block blue light.

Blue light gets more concerns in digital era, which is mostly emitted from digital device screen like iPhone, smartphone, tablet, TV, LED light, etc. It can hurt our eyes if we stare in front of PC for more than 3 hours. So blue light blocking apps and glasses are more popular now.

Answer 13

The reason inverted color setting exist is for people with low visablility or that are considered blind but can still see… hope this helps

See Microsoft's Accessibility Documentations

Answer 14

I am thankful for this question.

What I am going to say comes from personal experience. I am a graphic designer who has undergone eye surgery then became mostly a developer.

There are a few components to the question of dark on light VS light on dark which I think are not enough talked about:

The monitor itself has contrast

When I was doing mostly graphic design for printing, my monitor was calibrated at around 120cd/m2 with a gamma of 2.0 (importantly, it had a mat panel). This was very easy on the eyes and I would prefer a light theme for all of my apps. But most people have bright monitors with a higher gamma with which a light theme can rapidly become uncomfortable.

When you read light text on a dark background during the day, you can and often want to significantly increase the brightness and contrast of your monitor to a level which would be dazzling if the theme was light, simply because your monitor cannot produce enough light to compete with your environment. For the same level of comfort, a dark theme and a light theme are not used with the same monitor settings.

Text with vibrant colours is more readable on a dark background

If you have done some programming in your life you will have noticed that it is kind of hard to find a light theme with good syntax highlighting.

For a colour to be easily recognisable on a white background, it has to be of a minimum brightness, otherwise it just looks like darkish mud, because the perception of the colour of the relatively thin text is affected by the surrounding bright background. The same colour on a dark background would look more saturated.

Many theme authors avoid pure white backgrounds for stylistic reasons or because they want to reduce eye strain. The problem is that this reduces the difference in luminance between the text and the background. As a result, they can only increase the brightness of the text so much and they need to choose between good contrast and easily recognisable colours. This extreme use case can tell us a lot about colours in interfaces.

"Medium" themes exist in some applications, like Photoshop, mostly because medium grey is neutral an does not change your perception of your artwork, but the problem is that they can only be shades of grey.

The whole page matters

I can experience some kind of bloom/glow when I read a dense paragraph of white text on a black background, but this does not happen when I read a single word (except maybe just after surgery). I don't know of accessibility tools which take into account the relative size of the element under test, other elements surrounding it or the general balance of bright and dark areas of the page, but all of this affects accessibility and comfort for all users. Design is holistic, but tools are atomic.

I wish we had cleverer GPU software which can dynamically change the brightness of the screen based on the content: I hate exiting a dark theme app to be blinded by a white web page and vice versa, and I would appreciate "HDR pages" which can tune the contrast locally. BenQ does things like this with their CAD monitors to make thin lines more legible. This would be a great accessibility feature.

Answer 15

If you look at the data points on high contrast reading studies what you notice is more veriability on the high constrast side of chart. You will also notice that readability is not significantly lower on high contrast side. What that mean is some people find high contrast much more readable. This suggests that some people are well adapted to high contrast and others not. It also explains why there is so much controversy about this subject.

Answer 16

Those who have Dyslexia can benefit greatly with different colors. In fact they often use color overlay's when reading hard copies of books.

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To answer the questions below, what Gary is getting at here is that for a certain type of dyslexia (dyslexia is an umbrella term for unexpectedly low reading ability, not a specific condition), called Irlen Syndrome, coloured overlays are often used in order to reduce the glaring black text on white background contrast. It varies from person to person, but the most commonly successful overlays are blue and yellow. So his thinking is that inverting the colours could also help with this.

On a wider note, inverted colours are a cheap hack. What's actually beneficial is a properly designed high contrast color scheme, as seen in Windows and the XBox One.

Simply inverting the screen output is a way to get past of the way to that for little effort. But it isn't as effective.