If they are all the same species of neos, they will interbreed and you'll end up with a tank full of brown shrimp. You can call them "chocolate shrimp" if it makes you feel better. That's what I do. After a while large colonies of only a single color will also start to get lots of browns. Keeping them colored up requires catching and culling the brown ones as much as possible.
Actually it would result in wild types, chocolates are no where near the same as what the results would be. Kind of like saying you would get all painted red cherries from them cross breeding. Now if you want to call them brindle colored that may work for some of them but most will end up being a light natural colored shrimp.