dying hair
Should be fine. Hair loss at the root is different than breakage. If you are experiencing hair loss as a result of surgery, it's loss from the root - below the skin, where hair colour doesn't go. (And if you're doing it yourself be sure not to rub the colour in to your scalp) Unless you have damaged hair (dry, split ends, breaks easily) colouring it shouldn't affect it any differently then it it did pre-surgery :)
RNY on 07/17/13