Hair Homogeneity and heterogeneity question

[Montario]

Hello everyone

I have a question which I have been trying to find out for some time now. If one had blond hair from birth though only their head hair darkened by early adulthood, what genetic combination would they most likely be? I was thinking probably recessive bb or mabye Bb though I might be wrong. I understand there are more to play in the scenario then this but for simplicity sake which combination is most likely? Thank you in advance!

[biba56]

I'm not sure, but I would say they are heterozygous because their hair darkens in adulthood, which means they have some genetic information (one allele) for making melanin.

[JackBean]

Sometimes the light hair get darker only after exposure to light.

[Montario]

Sometimes the light hair get darker only after exposure to light.

If that was the case, would that mean that person would have two blond alleles?