damsels are not nano fish...
blue..? um...
pseudochromis flavivertex is a good one...
psudochromis fridmani or whatever it's called isn't blue, but it's super bright...
that's all i can think of that is a nano tank compatible that has en intense color close to blue...
also... do people really buy their fish this way..? like... i don't want a blue spotted jaw fish because it has yellow, and i don't want a yellow fish..? LOL... i thought people buy fishes based on temperament, tank size, and coral status...?