8% of males are colourblind [1]. If my maths is right that's roughly the population of the USA. A group worth worrying about I'd have thought.

[1] http://www.colourblindawareness.org

We almost that exact discussion at work yesterday. The question from one of my colleagues in customer service was: How is the customer suppose to know if the product is in stock, when they're on the checkout page?

Apparently our UI design decided to indicate that with red and green dots on the order line. If he had though about color blind users, normal users wouldn't have issues either.

> If he had though about color blind users, normal users wouldn't have issues either.

That's what you meant, right?

Anyway, that's exactly the argument I always bring up: if you design for the colour blind, the deaf, don't assume righthandedness, etc, and you do it well, the interface will end up more user-friendly for everyone.

In your example, adding a hint based on shape/position/lightness (or all three even) as well as a colour is easier to read for everyone. Similarly, using some verion of Cubehelix[0] is the more readable option for heatmap-scales, and again not just for the colourblind but for everyone.

[0] http://www.ifweassume.com/2013/05/cubehelix-or-how-i-learned...

>That's what you meant, right?

Yes, exactly.

Law or strong corporate policy tantamount to a law. They're too small a market otherwise.