I don't think it is saliva staining, as he has a slight touch of it on his neck hair too, where no saliva can reach! Plus it's only inbetween a few specific toes, not all of them, and I've never noticed him munching there over anywhere else. Our last cocker had pinkish fur around his mouth, which was definitely from saliva staining, but I'm not convinced that Henry's is. I also thought that the staining only occurred if the dog's diet had tomato pomace in it, and he's been on Acana Wild Prairie for 6 weeks which has no tomato pomace in it, and the hair's still growing ginger!
He's looking a lot less brown all over now most of his puppy fur has been stripped out, but still looks a bit brown when the sun is shining directly onto his ears and fluffy legs.