I also have a rose grey andalusian. After about five years of age she turned pretty grey but she fluctuates in colour a lot so the rose will still come out sometimes
She will turn grey, some will stay dark longer though, really depends on the horse. If she's 4 and still pretty dark, she probably won't fully grey out until 10+ but again, hard to predict.
I am seeing white hairs but she still has a lot of black.... oh well, fingers crossed.
By the age of 4 rose greys usually have a lot of white hairs mixed in. They also turn grey at very young ages. If you aren't seeing white hairs, and she has black points, mane, and tail, she'll probably won't turn grey.
It's very rare for a horse to stay like that in fact... She is a 4 year old Andalusian. But her mane and tail are black and so are her legs from the knee down. She has bay all over her and on her face and since her dam is dark bay I'm hoping she'll stay like that.
I have two friends who had rose grey horses, but they all turned grey. How old is she?