Here's my breeder's take on color in Labs:
Lab Lessons - Let's Talk About Color?
She breeds nothing but Labs, and she's been in the business for 30 or 40 years . . .
No, these appear to be a new thing... a mutation of some kind... they are silver, and look like Weimeraners.
http://www.silverlabs.com/
Well, I did see one, and a local lab breeder does have them.