I was playing with some puzzle ideas this morning, one of which involved messing about with different colours in a way which might be impossible for someone colour-blind. I won't go into details (spoilers!), but instead will make this a general question:

Is it OK to post puzzles which require distinguishing fairly similar colours in order to be solved?

For instance, let's say one step in the solution involves looking at a bunch of objects which are almost all of the same green colour and selecting those which are a slightly lighter shade of green in order to find some hidden message. This would probably not be doable by someone who's colour-blind.

I'm sure I remember seeing puzzles here which do involve this sort of thing, but I couldn't think of any off-hand. On the other hand, I've also seen at least one recent puzzle which underwent several edits just in order to make it easier for colour-blind solvers, so I thought it was worth a meta for this.

On the one hand, obviously we want to discriminate as little as possible. On the other hand, we have a lot of puzzles which would be completely unsolvable for, say, blind people, and I doubt anyone would call for abolishing the tag just for that reason. Does it make a difference that one of our active users (I don't recall who) is colour-blind, while as far as I know none of us are blind? Would it solve the problem to simply create a tag which colour-blind users could put on their ignore list, in the same way as a hypothetical blind user could ignore the tag?

  • 1
    $\begingroup$ meta.puzzling.stackexchange.com/questions/5142/… $\endgroup$
    – Mithical
    Nov 23 '16 at 15:04
  • $\begingroup$ So you mean questions like these? (1) (2) (3) ...Which just all happen to be mine? $\endgroup$
    – Mithical
    Nov 23 '16 at 15:53
  • 2
    $\begingroup$ It's worth considering that the ability to visually distinguish between similar colors is extremely dependent on the user's screen, and may not be dependable anyway. $\endgroup$
    – user20
    Nov 23 '16 at 19:24
  • $\begingroup$ @IAmInPLS I used your wording originally, but changed it before posting so that the bold bit would fit on one line :-) </ocd> $\endgroup$ Nov 23 '16 at 23:53
  • $\begingroup$ @Mithrandir I didn't have any of your puzzles in mind when writing the question, no. $\endgroup$ Nov 23 '16 at 23:59
  • $\begingroup$ If you want to check if your puzzle is good for color-blind people, there are a variety of "simulation" tools on the net which convert colors to give you an idea. (I've used an iPad-app in the past to create a puzzle. Sorry, don't know the name anymore.) Also, it is a worthwhile read to inform yourself on the various color-illnesses and hence recommended colors for use in graphs etc. If PuzzlingSE add to the awareness of the problem, it just made the world a slightly better place :c) (In fact, dealing with color in puzzles made me make changes in some software to help. So it already did.) $\endgroup$
    – BmyGuest
    Nov 24 '16 at 8:12
  • $\begingroup$ Many systems have a Color Filter that can adjust color output to make it look normal to colorblind users. $\endgroup$
    – Peanut
    Dec 5 '16 at 20:48


It is "OK" as far of the rules of the site go. There is nothing that says that you must accommodate colour-blindness (or any other disability).

That being said, it is certainly worth considering colour-blindness and other disabilities when constructing your puzzles. If the actual colours don't matter, try to use colours that are easily distinguishable by anyone. If you have an image containing only text in your puzzle, provide a text-only version for those who can't view images. The list goes on.

It is always good to be considerate of others' needs and abilities, but I don't think that should preclude you from posting a puzzle that isn't accessible to everyone.

It may be worth putting a disclaimer at the beginning noting that the puzzle may not be solvable for a colour-blind person. (Or consider using shades of blue instead of green.)

(Also, note that if you are only using shades of a single colour (e.g. green with more or less black or white), it should be equally distinguishable to a colour-blind person. It's only when your puzzle requires distinguishing between red and green (or colours that contain them) that it could be problematic. (Or, in more rare cases, between blue and yellow.))

  • $\begingroup$ Thanks - this makes sense. (Re your last 1+ paragraphs in brackets: I don't know much about exactly what colour-blind people have difficulty with, so this is something worth learning before I embark on creating an Alconjian or BmyGuestesque visual puzzle. I'll ask Deusovi.) $\endgroup$ Nov 23 '16 at 23:58

I like to pick this up, as a couple of my puzzles (this,this) rely on color, color recognition, and or color properties.

In fact, a very recent puzzle of mine uses exactly the question raised as a key-part of its solution.

I’ve not yet written a “follow-up” for it yet, because it is not yet solved, but the idea of “color blindness” actually inspired this puzzle part. I wanted to create something which makes color-aware people experience the situation of being color-blind. (i.e. Missing out on information without being aware that they are!)

Obviously, changing the colors or tagging the puzzle to point at the colors would have spoilt that attempt to death. However, once discovered (-or spoiler-tagged by “strong hints”-) a courtesy-download of “visually more distinctive” images can be provided for the remaining puzzle (which you might want to solve – hint, hint.)

So, is it it OK to use faint color differences?


When color is an integral part of the puzzle, it is legit to use it.
In the same way, as it would be okay to use a word in a word-puzzle that is only known to subset of puzzlers, or to center a puzzle on "d" vs "b" for a dyslectic person.

Are colorblind people handicapped for those puzzles? Yes, they are. But luckily, in our digital age, they are no longer prohibited from those puzzles.

Even the faintest color difference is visible as a distinct digital number and both manual investigation as well as digital enhancement/changing is possible.

Yes, it adds another “difficulty” dimension, but for certain puzzles of the past, the difference between colorblind and not colorblind didn’t really make a difference, when one needed to look at the color code values anyhow.

Having said that, like with most things, color should be used ‘responsibly’ and with ‘thought’.

If there is no inherent need for a specific color hard to distinguish by colorblind people, then it is courtesy to choose ‘better’ colors - it just makes your puzzle better and opens up to a wider audience! (Including non-color-blind people, who want to black-white print any such puzzle for offline use.)

This particularly applies to puzzles where color is used to easily distinguish similar items so they can be brought into some other logical context. It is a clear improvement to use colors which also work for people with color-blindness. It can be even better to use different shapes/symbols in addition.

BTW, there is also a puzzle which has color blindness as solution. :c)

  • $\begingroup$ Thanks for your input! I've noticed that quite a few of your puzzles involve doing interesting things with colours (which isn't a criticism, of course - you're one of the best puzzle makers on the site). $\endgroup$ Nov 24 '16 at 16:11

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