What causes the 'splash' bird to appear when breeding Blue Andalusians together?

Answer

It is a direct result of carrying two copies of the dilution allele ($ ext{Bl}^+/ ext{Bl}^+$).

The splash bird appears because it carries two copies of the dilution allele, which is an expected outcome when breeding two birds that already carry one copy of the dilution gene.

What causes the 'splash' bird to appear when breeding Blue Andalusians together?
colorChickenbreedAndalusian