I am building an app which uses some nice calm green and yellow colours.
However, on the iPhone 5 'yellow screen' theses colours lose their charm and are actually quite sharp.
My question is: is the iPhone 5 yellow screen so common that I should accept it, and design for it?
There doesn't seem to be any clear answers out there. Would appreciate some other developer / designer views on the situation.
You won't get any definite info about how much iPhones do have the yellow screen issue. The only one who can have this information is Apple and they surely won't give it out to the public.
My guess is, that there are relatively few iPhones with that problem since people who have the issue will report back on forums, while people without won't. Even if it's 20% of all devices (which I doubt, my guess would be something like 1-2%), I think it wouldn't make sense to adjust your design for those devices, unless you already have one in mind that's as good as your current one.