if you like the activity Kaylee described, take a look at;
Royal Black Emperor Tetra - Nematobrycon palmeri
which I have a school of, and behave similar to blues.
their coloring changes from orange to blue when light hits them from different angles.
as they mature their fin tips darken, and males eventually get longer more elaborate fins.
they like to school against a water current in a clear unobstructed area of the tank.
mine are not territorial, but they are curious and clever similar in nature to tiger barbs.