I actually think the color is from the effects of the experiment. Kind of like how Rogue's hair turned white from stress, I think Pietro's hair might have turned white in the same way. <<< yes I like that theory. It was in actuality caused by Aaron Taylor-Johnson's insistence for keeping Pietro's hair white like in the comics (go ATJ!!) <----- ooh this all makes so much sense
You know maybe if the movies didn't make rogue feel so awful about her powers they wouldn't be so bad. Because in the comics rogue is completely fine and she uses her power to her advantage. Not that she doesn't complain about it time and time again but at least the comics show the real rogue, and how she really knows how to make the best of her powers.