As far as i could know, stress don't causes sore eyes. So too much anxiety won't affect your eyes unless you always rub your eyes. Besides, i heard that the soreness of the eyes may be caused in some eye disorder such as blepharitis, allergy, dry eye or infection exists etc. So, check your eyes if get dry or infection etc. Only you know the reason why sore eyes happen, you can make the right treatment.
Yes, it could happen to a few people. The color of our eyes is controlled by the quantity and color of pigment granules that is melanin in the stroma. Compared with skin and hair, our eyes don't always synthesize color pigment, but keep the accumulated pigment in the stroma. However, only a few people could change eye color when they are aging based on two main reasons, one is disease unfortunately, and the other one is genetics.