The color variations don't really come from crossing but mutations that are selectively bred. EG, yellows and greens come from red cherries, which in a turn are a mutation of the wild Neocar. shrimp. They are normally clear almost with a hint of brown through the body. Through breeding wild ones over and over they would notice a red tinted one out of those, and after getting some of those, they only bred those till they got redder and redder ones. Once they started breeding red's for a while, a yellow or green one would pop up in the population, and they in turn were removed and only bred with others with the mutation.
Crystal shrimp all come from breeding of the Bee shrimp, which are mostly black and bits of white and clear. They were bred to get whiter and black ones and then a red and white one popped up in the population and that was kept out and bred with more and more blacks until another red one came out. Its said that pretty much all red crystal shrimp come from that 1 red mutation, probably out of millions and millions of shrimp. Same with the different patterns and grades of the shrimp, 1 came out more white and less red and was bred with more and more to get another one, then those were bred to mostly only produce that pattern if you want.
Tiger shrimp, same thing.
If you want to cross and red and yellow, you won't get a orange, you'll get a wild color which is clear and tinted brown. Most of these colors are recessive gene mutations and crossed with a wild cousin related to them, the wild dominant genes will kick back in and kill the coloring. The best way to get something is selective breeding but this is done on the scale of breeding million of shrimp for many generations to get 1 that looks different and then trying to keep that gene going.
