Here's why:
* Labrador Retriever coat colors are determined by two genes: The B gene determines black vs. brown, and the E gene determines whether the pigment is expressed (black/brown) or diluted (yellow).
* Yellow Labs can carry recessive genes: A yellow Lab can carry the genes for black or brown pigment even though they express yellow.
* The combination of genes from both parents determines the puppies' colors: If one parent is yellow and carries the gene for black, and the other parent is black, the puppies could be black, brown, or yellow.
To determine possible puppy colors, you need to know the genotypes of both parents (which genes they carry).
A veterinarian or a knowledgeable breeder can help you understand the genetics of your Lab and predict the potential color combinations of the puppies.