I am a mutant. I was bitten by a radioactive spider during a school trip and… I’m lying. I don’t have any superpowers, I’m just colour blind. I’m not full on grey scale colour blind, I am Tritanomalous and Deuteranomalous, or more simply I am red/green and blue/green colour blind. Being colour blind has a very negligible effect on my life, 99% of the time I don’t notice and it doesn’t matter when I confuse colours. Notable exceptions include the “green” light on new style temporary traffic lights which I perceive as blue, the coloured bands on resistors (again, apologies to the electronics lab tech during my time at uni) and my trainers with the “blue” strap on them – my Mum requested this one was added in after I had her spend an afternoon looking for trainers with a green strap.
Anyway, enough about me, this post is for you. Okay, a little bit more about me first… I am a software/web developer and because I am colour blind I am aware of certain issues/limitations which other folk will often completely fail to consider when designing User Interfaces.
Colour Choice: Lets start with the biggest potential mistake: colour choice, you need to consider where colours are in the spectrum. I found this website which allows you to generate and compare colour palettes, but it has the added bonus of allowing you to see how your colour scheme looks to people with the various flavours of colour blindness. What looks complementary to you may look incredibly odd, or worse still completely identical, to me.
Colour Mass: But it’s not just about colour swatches, you need to consider the amount of colour that is used because colour mass also effects perception. A thin line of a certain colour may actually appear as black to someone who is colour blind, whereas a slightly thicker line will be able to be perceived without problem. In exactly the same way, colours can get lost in the “noise” of other colours if too many are grouped together.
Texture: Another important point to consider is that the texture of an item can really effect how a colour blind person perceives it. A printed design mock up can look completely different to the design as viewed on a screen, and different again when viewed on a different screen. Textures and materials do effect colour perception.
Consider this post on “Better car brake lights” by Mark Cossey. Hopefully you can now see that using escalating colours to indicate how severely the car is decelerating would be dangerous, whereas flashing lights would be without problem to the majority of colour blind people. This is why in general, I don’t think that you should ever use colour alone to present information to users, an additional albeit slight change in appearance will make your design much more accessible to both colour blind and regular sighted users.
Armed with the information in this post, you should be able to appreciate the absolute best thing about being colour blind: some forms of camouflage are completely ineffective when used against colour blind people. If only this applied to Call of Duty!