# What colours should arithmetical operators +, −, ÷ and × have?

Are there any colours that are commonly associated with basic arithmetical operations?

I want to make the operators +, , ÷ and × more easily distinguishable by colourizing them. For the plus and minus operators the solution is probably using green and red. But what about division and multiplication operators?

I thought there might be some standard for pocket calculators. I found a few with a blue and a few with a green plus key, but didn't see a consistent pattern. Are there even any colours that can be associated with those operations or doesn't it matter what I choose?

Update: The question raised while testing a logic/math puzzle game prototype, where there are tokens containing those operators. They are a central part of the game and there are only a few numbers. I'm convinced colours will be very helpful to spot the operators better. I think of either colouring the background or colouring the operators themselves - maybe mixed, a consistent background colour for all operators, another one for all numbers). Size has to be consistent. Due their button like nature (squares for now) they reminded me of a calculator, so that's where I started.

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How important is this? And what is the real reason for it? Ask you yourself the 3 Why?'s because maybe it will unfold into something different. Good questions lead to better answers. – JeroenEijkhof Nov 20 '11 at 9:50
@JeroenEijkhof Updated the question. What 3 Why?'s are you referring to? – kapep Nov 20 '11 at 12:32
@Erics Haven't decided yet to use the ÷ symbol for division. I think a slash would be more consistent (it's a rotated , just like is + is a rotated × ?). Anyway it looks better with this site's font, unlike / or so the edit is ok. – kapep Nov 20 '11 at 12:37
I believe @JeroenEijkhof might be referring to the 5 Whys, often used in root cause analysis. – Thomas Owens Nov 20 '11 at 16:11

Talking about semiotics, I don't think there are global or even local color relations for mathematical operations (if you want to go crazy on that, you can do some research on people that have a medical situation called "synesthesia". People with this situation associate thoughts and physical senses with colors and flavors. Yes, this is totally insane). hehe

But I got a more plausible solution for you, but I guess it relies half on simple logic and half on semiotic:

• as you've said, it's common to relate cold hues to addition (+) and hot hues to subtraction (-) by a simple cultural succession.

• multiplication (x) is basically a sequence of additions. so, it's somehow related to a stronger version of +

• division (/) using natural numbers usually results in smaller numbers and can be seen as a stronger version of -

on the "addition couple" you can pick a green color and play with shades (giving multiplication a more saturated green) or just use different cold colors (i would suggest green for the + and blue for x, since blue is a stronger color)

the same applies to the "subtraction group", but you should use shades of red or just a pair of orange (for -) and red (for /)

sorry for the crazy stuff, but that's what I would have done! good luck!

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There are no color standards for this.

If your goal is to make operators visually distinct, then:

1. Make all numbers, variables, and other symbols the default color (eg, black)
2. Make all operators some special color (eg, green)

Adding more colors will only confuse people. The scheme should be simple: a special color for operators so they stand out, and the standard/default color for everything else.

People will not understand any color scheme you invent. For example, if you make + and - one color, but * and / another color, the reason for that will not be apparent to people.

Don't overthink this. Pick one color and use it for all the operators. Then you're done.

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Good points. For normal expressions I would do just what you described; sticking to common syntax highlighting. I was thinking more of buttons containing the operators though (hence the calculator example). Updated question. – kapep Nov 20 '11 at 12:18
"Don't overthink this". I gotta put that on a poster for the office. Hmm ... what colour and font will I use ;-) – Erics Nov 21 '11 at 5:41
@Erics The phrase makes me think of white Helvetica on a black background. – Camilo Martin Dec 28 '11 at 13:57

Browsing through several hundred calculators on Google Images tells us that there is indeed no consistent pattern in actual colour. I think we can draw some reasonable conclusions from calculator manufacturers who should have done at least some research into this area, although statistically, (also depending on functionality and quality), there are likely to be a few calculators that will have had little thought put into them.

The + button tends to be larger quite often which makes sense as it's the most common operator. = frequently had a larger size as well.

The group of + − × ÷ and = is quite often a different colour to others - as are the set of digits - but the point of interest is that they are not necessarily a specific colour, but a contrasting colour.

In maybe just a few percent of cases, the + and buttons were found to be a different colour:

In 2 cases, the only variation was + was blue

In 2 cases, the only variation was - was red

In 1 case, + was blue and - was red

In 1 case, + was black and - was red

In 1 case, + was red

From which we can continue to conclude that there is no consistent pattern and that contrast is more important than actual colour

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