It will have to grow out, yes. But (not to alarm you) it may not go away entirely.
Quigley has some very light cream colored and some white areas around his lower lips and in certain places they are always stained. I think it comes from subtle irritation on the inside of the lip folds that causes more moisture to be present there, which never really dries up. It's kind of difficult to explain, so I'll try to take a photo tomorrow. I manage this by clipping the affected strands short, so they are usually hidden below his upper lips.
He will have the same staining going on in other areas when he has his seasonal allergies and licks (e.g. the inside of his elbows, between his paw pads, and on his lower belly).