If so, she's a gray tobiano, who will eventually turn either white or fleabitten (aquiring more very small, dark freckles) in her "blue" patches. And she's also not a Thoroughbred, or at least not a purebred one.
Thanks guys! And yes that is my mare. I know she's not a purebred thoroughbred - only put thoroughbred as there was no option for cross breeds. She is 3/4 thoroughbred and 1/4 welsh cob. Are you certain she will change colour? As I met her 12 year old mum who was still blue and white. Unless you mean she will change in her much later life?