I'm not aware that blue velvet shrimp loose their colour.
They're a darker colour variation of the blue jelly shrimp, Neocaridina davidi, I think, which is what I have.
Personally, I think the blue velvets are a bit too bright, but I've been wondering about investing in a few to see if I can get a more medium blue shrimp.
I'm not sure if shrimp genetics work that way though? Or would I just get mix of light and dark individuals? Is either light or dark dominant or recessive? Anyone know or like to take a guess?