Modern Pashtun men do not wear bright colours. With modern dyes and fabrics, they will wear the full range of pastels (even pink!) but never bright colours like red. I have a couple of red shirts that I wore once, then put away - bright colours are associated with women here. Off-whites, browns, light blues, light and dark greens (but no lime!), black, khaki and similar shades. White only for those who can count on not getting dirty.
Not sure how much current trends translate to the nineteenth century, but I can't paint bright colours on Afghans any more!