• About Colour Blindness (this page)
  
  What is Colour Blindness?
  Life with Colour Blindness
  Links
• Medical Terms for Colour Blindness
  
  Red-Green Colour Vision Deficiency
  Total Colour Blindness
• Colour Blind Design Hints and Tips
  
  Web Page Design for Colour Blind Readers
  Real-World Products for Colour Blind Customers

What is Colour Blindness?

At the back of your eyes you have Cones and Rods. Cones pick up colour. Rods pick up brightness. There are blue cones, red cones and green cones. They pick up different wavelengths of light. Colour blind people have less numbers of particular cones than normal, so they get colours confused. Some people are more colour blind than others.

I am very red-green colour blind (the medical term is Red Green Colour Vision Deficient), so I haven't got enough red and green cones (the latest scientific research suggests I have no green cones at all, but my red cones can pick up some green). This doesn't mean I see in black and white, or blue monochrome, but it does mean that I confuse red, green and brown colours, and also blue and purple. But this all depends on the intensity of the colour and the brightness of the light conditions at the time. For instance, I will always be able to tell that a bright green crayon is green, if I'm standing outside in bright sunlight. But if I'm standing under a 40-watt bulb then I might think it's a brown crayon. And if it was a green object which wasn't as colourful as a crayon, I could even think it was red.

Here are two identical pictures of random dots. Well, that's what I see them as. If you're not red-green colour blind then you will see a green number 17 in the picture on the left. I still can't see it even after my fiance traced it out.

Red-green colour blindness is a hereditary genetic disorder which affects one in twenty white males (red-green colour blindness rarely affects females or non-whites; total colour blindness affects less than one in a thousand of all sexes and races). That's more that the total proportion of all ethnic African, Asian and Oriental people in the UK! Yet very few companies or services give colour blind people any thought. We have instructions telling us to "press the red button", machines which have a green safety light and a red warning light, even colour-coded pills! I have to place a radio next to my mobile 'phone charger to find out whether it's fully charged or not (red light or continuous loud radio buzz: charging, green light or intermittent radio buzz: fully charged). At least traffic lights in the UK have a white rectangle around them so we can tell that they're traffic lights (light at top of rectangle: stop, light at bottom of rectangle: go) and not street lights (red and amber traffic lights look the same colour as yellow street lights, and green traffic lights look the same colour as white car headlamps).

Just imagine what an outcry there would be if all ethnic African, Asian and Oriental people were banned from playing Laser Quest! But that's what has happened to colour blind people (okay, we're not actually banned, but due to the design of the backpack lights, we can't participate in team games).

So, next time you write some instructions, or design some software, or colour-code somthing, think about the one in twenty white males who may not be able to understand it!

Please, please, please do not ask "What Colour is this?" whilst pointing to a item of your clothing. It's very rude and very boring. For example:

Andrew: "I'm colour blind. Can you tell me what colour this shirt is please?"
Clothing Salesperson: "Wow, you're colour blind! What colour is this, then?" (points to her jumper)
Andrew: "I don't know, I just told you I'm colour blind. Are you stupid or what? It looks (pick at random from red/green/brown) to me."
Clothing Salesperson: "Wow, you really are colour blind, it's (insert very specific word which means poo colour) actually. Ha Ha Ha."
Andrew: "**** off." (leaves shop without purchasing shirt)

And stop telling me how beautiful the sunset is!

And yes, I can see the bright blue flashing police light, I'm colour blind not totally ****ing blind, you idiot! AARRRRRRRRRRRRGgggggggggggh!

Nash Design's Color Vision Guide - sells colour vision testing cards online for education and general interest, and copyright owners of the "17" image used above.

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