I have two differents color micropeltes, one is grey, and other is black...why?

I can see two variety color in some micropeltes... some micropeltesare paler and others more colorful and bright. why? different geographic population?, different sex, different genetics? or why?
Variety grey

Variety Black tornasol

I can see two variety color in some micropeltes... some micropeltesare paler and others more colorful and bright. why? different geographic population?, different sex, different genetics? or why?
Variety grey
Variety Black tornasol