Can palettes be unambiguous for colour blind users?

Question

I am making design recommendations for a piece of software that wants to accommodate entirely illiterate users. A suggestion that has been made is to assist these users by employing "color coding" on key parts of our UI, so they can learn colors rather than learning the position or shapes of icons or words. We would need four colors to do this, and it would be in addition to other cues like labels.

Something like this:

Because our users are primarily male, it seems especially important to use colors that will not cause difficulties for color blind users.

Palettes developed for color blind users seem concerned only that each color can be seen as different. This is useful in charts and infographics, because a key or legend can always indicate the meaning of each colour. Such as this palette by Martin Krzywinski, uses only colours that don't appear identical to color blind users.

However, since our users will be given instructions like "select the green one", I wonder if this could cause confusion because, even though a CB user can tell the "purple" and "green" palette colors are different, they seem to differ primarily by lightness and could easily be described by either name.

To clarify this point, I made the image below. The larger circles are colors taken directly from Krzywinski's palette, and the small circles are examples of non-palette colors I have made that could be described with the same name.

From a CB perspective (bottom row), the questions "is this purple?" and "could this be blue-green?" seem impossible to answer with certainty.

Are there any ways to work around this ambiguity problem? Or is this color coding approach unhelpful for color blind users?

Answer 1

Since

• Your users are entirely illiterate
• Your users are potentially colour blind
• You only have to display four distinct options
• You are able to issue verbal instructions to your users about how to use the system. (I am assuming this, from your statements.)

My suggestion is to use a combination of four abstract shapes with distinct colours, as shown.

This way, you can tell users to "click on the yellow circle", or "click on the green triangle" as appropriate.

Answer 2

From my past experience doing technical writing and instructional design, the key to writing unambiguous instructions is to structure it around the process first and then provide the details. So you would actually break it down into a hierarchy like Goal > Task > Step so that you are only providing specific details at a smaller part of the instructions where it is more likely to change (i.e. even if the step changes the task might not change, and even if the task changes the goal is probably still the same).

In this case, you instruction of pressing the button is a step in a task that needs to be completed in order to accomplish a goal. One way is to simply provide the instruction followed by the detail, which would be written as: "press the button (image or description)" instead of "press the button".

I would assume that even illiterate people will have more than one way of learning/recognizing information using visual cues, so the use of color alone is going to work well for a portion of the people. However, if you combine a color with a shape (and/or icon) it would probably be more helpful to a large portion of users.

So while I don't think there is an issue with using a CB safe colour palette so that they can distinguish between different buttons (maybe you have to pick colours with more contrast/difference), it does mean that you might need to write your instructions differently to be easier to interpret and understand (i.e. less ambiguous). To save you some headaches it may be preferable to introduce at least another visual cue.