I always have a hard time iding some kinds of severums if they are small. This guy is about 2". The picture doesnt show his color but he has orange tint in bottom fins and top fins have a very very slight blue. his pectoral fins and jaw line has a bit of orange as well , thats why i thought it was rotkeil, so is it? thanks 
Rotkeils are more elongated than "regular" sevs; more obvious when you have them in the same tank.