They would most likely revert to natural coloration, which in the case of the red/yellow and blue pearl/snowball shrimp is brown. So you get unattractive offspring. (If you like the brown look, it's possible to find wild-type Neocaridina heteropoda) Also, you won't be able to sell the offspring without letting people know their background, and a lot of people won't want to buy hybridized shrimp because they won't breed true.
Basically if you let them hybridize you're undoing all the work of all the generations of breeding to get the specific color you have.
Some people don't really care if their shrimp hybridize, and you can do whatever you want with your own tank, but if you started with a tank of yellow and red cherry shrimp, pretty soon you'd just have mostly brown ones.
Of course, crossing different kinds of shrimps is how some new color morphs are discovered, but unless you have a breeding setup with a lot of shrimp, you're not really going to be able to come up with any usable new colors/patterns.