The lacing genes are complex and require 4 different genes, miss even a single one and you don't get any lacing at all. And the solid black pattern of the Splash is very dominant. Second generation would have better odds of having both the blue gene and lacing.
Cornish Cross are bred for meat. The Cornish breed is entirely different. They are very cold hardy. Not the greatest layers, but decent. They do have a tendency to go broody, and make excellent mothers.