If you crossed a Blue Ameraucana rooster with a Blue Andalusian hen, the offspring's plumage could be blue, black, or splash. Blue is a dominant trait in both breeds, so there is a 50% chance that the offspring will be blue. Black and splash are recessive traits, so the remaining 50% will be a combination of the two.
As for egg color, both Blue Ameraucanas and Blue Andalusians lay blue eggs. So, it's likely that the offspring will also lay blue eggs. However, the shade of blue may vary depending on the genetics of the individual offspring.
It's important to note that breeding chickens involves a lot of variables and can be unpredictable. The outcome of the cross can be influenced by factors such as genetics, environment, and chance. So while there's a good chance that the offspring will have blue plumage and lay blue eggs, it's important to keep an open mind and be prepared for some surprising results.