> Why in the world would colors discomfort you if you can't discern between them?
Because pretty much as soon as one starts colour coding items in the UI, people start using the specific colours to encode meaning. If your UI requires someone to discern between the red and green versions of the same icon in your UI twice, congrats, you just lost 8% of male users!
> Would a pedestrian traffic light be better if it wasn't color coded?
If they weren't colour-coded, they would have to be differentiated by shape, and then when I traveled to Canada, I wouldn't have to guess whether the fancy horizontal traffic lights are ordered left-to-right or right-to-left
> Would a white car be preferable to a red car?
Even fully colour-sighted folks can't see red very well at night, so yes, white car > red car
With that line of reasoning we arrive at the conclusion that all graphical elements of an interface should be removed, as the blind cannot see icons.
> If your UI requires someone to discern between the red and green versions of the same icon
Color coding has never been about this, only when implemented wrongly. It is just an extra differentiator for GUI elements which are already differentiated by icon shape and text labels.
> Color coding... is just an extra differentiator for GUI elements which are already differentiated by icon shape and text labels.
In principle, I agree, but I do not believe I have ever used a software package that follows this philosophy. In practice, once you give people a tool, they are inclined to use it, and most projects only try and address accessibility concerns post-ship
Personal anecdote re the traffic lights: I thought "green light" was a metaphor until sometime my twenties, when a friend explained that the 3rd light actually is green to other people. It's always been a white light to me
Because pretty much as soon as one starts colour coding items in the UI, people start using the specific colours to encode meaning. If your UI requires someone to discern between the red and green versions of the same icon in your UI twice, congrats, you just lost 8% of male users!
> Would a pedestrian traffic light be better if it wasn't color coded?
If they weren't colour-coded, they would have to be differentiated by shape, and then when I traveled to Canada, I wouldn't have to guess whether the fancy horizontal traffic lights are ordered left-to-right or right-to-left
> Would a white car be preferable to a red car?
Even fully colour-sighted folks can't see red very well at night, so yes, white car > red car