White flights (on any color Guinea, except pure White and Pied) are a considered a flaw/fault according to the "Proposed Guinea Fowl Standard of Perfection", tho some breeders say that white flights means they are carrying a little bit of the Pied gene. In my experience one bird with white flights bred to a bird without any white flights will produce a few offspring with white flights, but not all, and breeding 2 birds with white flights will produce more offspring with white flights, but still not every keet will mature with white flights. I have never had Pied keets hatch from a pair of adults that both had white flights... (so I'm still on the fence about white flights being related to the Pied gene, based on my personal experience).
IMO, white flights just equate to bad breeding stock unless you are breeding a pure White bird to a bird with white flights and wanting Pied keets, then it does not really matter). The best way to avoid white flights in future offspring is to keep all Pieds and any birds that have white flights out of your breeding flocks. If you are going to buy keets locally be sure to ask to see the parent birds of the keets (or flock) and inspect for white flights, and if you are going to buy keets from a hatchery it's a good idea to call and ask them if their breeding stock has white flights or is prone to hatching keets that mature to have white flights.
Guinea Hens can be bred, carry the male's sperm in their bodies and fertilize eggs with it for about 2 weeks from just one breeding, but generally breeding pairs or breeding flocks are kept together and allowed to breed frequently to make sure fertility stays high.
Your almost pure black Guinea is most likely a Royal Purple... and when bred to a Lavender Hen the dark color gene (charcoal grey/black) will be dominant over the lighter color gene (blue) of the Lavender, but the fully-pearled gene of the Lavender will be dominant over the partially-pearled gene of the Royal Purple... which will most likely result in mostly Pearl Grey keets from the hatches. Depending on which hidden recessive genes both birds are carrying you may get a few Lavenders and Royal Purples too, maybe even Coral Blues and an occasional surprise color but realistically you can expect the hatches to be dominated by Pearl Greys.
