I know some that tend to "brown out" or even lighten up.
Blushing?? Hmm good question. Maybe someone else might know better but I would think that it would not show age by the blushing more or less..
This is my un-educated guess
I've noticed the blushing gets more noticable with age. I'm not sure if it is because they really get more blushing, or just that as the snake gets bigger, the blushed areas get bigger and thus more noticable.
One of these days I'll have to go back and compare some baby pics.