Why is my pit bull puppy coat keep changeing colors!!?

I have a 9 month old pit bull pup she was dark chocolate from 2 months all the way until 5 months then she started to get fawn high lights on her rear part and sides and feet now she just turned 9 months and her legs were fawn now there turning back dark chocolate what is the reason that this is happening also her dad was blue and mom was chocolate and the fawn wasent red fawn it was blue fawn? why does she keep changeing colors?