I have this filly that I think might be sooty she has dark patches on her back legs kind of like this

but she hasn't got any black in her mane it is a light brown colour She is registered as bay but haven't got any black points her sire is Piebald her dam is chestnut and white
And this is her not a good picture I know as you can't see it very well as she is in her winter coat but I have lost my camera so can't get any better ones but you can see the back leg is darker, right now it looks light she has her mane liver chestnut colour then she has splodges of a bay red colour.

https://fbcdn-sphotos-h-a.akamaihd.n...06434162_n.jpg
Anyone got any ideas what is going on?