Bichon/Maltese hair color

Question
My dog seems to now have a beard!  He is 15 months old an until about 4 months ago he was all white.  Now has a brownish/reddish beard all around his mouth.  Can this be the result of his diet or playing outside in the dirt or saliva?  My children and their friends keep asking why?  Please advise.

Answer
This could be a result of dyes that are put in some foods, if that's the case I would put him on a high quality dry food.  It could also be a result of saliva and dirt, you should clean his face daily with something like a warm wash cloth or baby wipe and when you bathe him use a whitening shampoo.  If you can't get rid of the staining you should at least be able to prevent it as the hair grows out.  Let me know if I can be anymore help.