odd colouring? not sure what it is.

[BSJAlove]

My little NF is a really light/dull chestnut and lately, the top of his legs are going dark grey and hes getting black spots all over his bum! his tummy is greying out at the bottom. its just odd! ill have to get a photo later but hes 5 years old. what is it? thank you

 

[Natch]

Will have to wait to see the photo, but how long have you had him? Sometimes horses do really odd things with their coats throughout the year, I knew a welshie who was bright bay, and developed zebra pantaloons every autumn