[TimEricsson]

That can occur for a number of reasons. How old is he? When pups shed their "puppy coat" their adult coat can sometimes be a shade or two different.

It also can occur when a dog is shedding winter fur... the dead hair turns a lighter colour than the living hair. When my seal and white bitch blows her winter coat, she looks like a merle with how patchy her seal gets And my red puppy looked merle and brindle all in one when he was blowing his puppy coat AND winter coat at the same time! So, I wouldn't be too worried