Brussels Griffon black hair w/ grey undercoat

Question
QUESTION: Hello!  I have a 4 month old black and tan Brussels Griffon puppy.  I noticed about a month ago the hair on top of his head has a grey undercoat...  my baby is suppose to be a black and tan.  His tan markings are where there suppose to be but the grey undercoat is worrying me.  Do you think the hair will come in grey and the black eventually gone? I'm hoping this is just puppy undercoat and once hand stripped the black will come...  your thoughts??  Thanks!

ANSWER: Stripping will definitely help this, but you do need to keep raking that undercoat out. What I do with my youngsters now is to put them in the tub once a week, shampoo them up, and then taking a grooming (lava) stone to them while they are suds-up. The stone pulls out the longer hairs and the undercoat quite easily this way. Be sure you have a *good* strainer in the drain if you try this.

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QUESTION: So do you think the black hair will come in once the grey is raked out?  
Thank you so much for you quick responses, you're awesome~

Answer
I would start stripping on that head now to make certain that there is black hair coming in, while trying to cut down on the undercoat at the same time. The fact that the undercoat is light there at such an early age is not a good sign, and you may end up fighting with that his entire life.