I asked the lady I got my eggs from. She breeds blue with splash. Out of 8 chicks that hatched from those eggs, 7 are pale grey and one very very dark grey. Are the pale grey blue or splash? At what age can I tell? Why are they all coming out the same color? Is there something about the genetics of the other colors that makes them weak, maybe not strong enough to hatch? I know this sounds crazy, I just can't think why only the dark ones don't make it. The only dark one that hatched, died a few days after hatching. It wouldn't eat.
With tht small a number, you can't make an assumption like that. Percentages don't old up unless you hatch a large number of birds; with only 8, it is pure chance that 7 came out the same colour, and only the darker one would not eat. Do you have photos?