Splash Cochins are an attractive sooty-white with dark splashes of grey. The amount of dark flecks will vary from bird to bird. This colour is not yet an APA standard variety for large fowl Cochins, but it is recognized in the Bantam size.
About Blue genetics...
Splash chicks are produced from blue matings because of the incomplete dominance of the blue feathering gene which dilutes the black. Simply put, when two blue chickens are mated together, their progeny will not all be blue. Chicks with two copies of the gene have near-total dilution and are splash; those with no copies have no dilution and are black. Only the ones with a single copy will have the partial dilution necessary to produce blue plumage.