hey, does anyone no if the was a reason as to why krisyen got her hair dyed 或者 was it just for the sake of doing it

If 你 mean the dark and short hair like the picture below, it was for a movie.
Kristen is playing Joan Jett in a new movie called The Runaways, so she has to look the part.

i heard it was for her new movie "on the road"
not sure though

Yes, Kristen is playing Marylou in On The Road, and the character requires her to lighten her hair.

i think she may just needed a change all women are like that now and a gain