Tiger barb behavior?

I have 8 tiger barbs that I bought about 2 months ago. They were very
small when I got them, their body size was about 3/4" or less. They are
growing very fast as they are now about 1 1/2" to 1 3/4". Sometimes they
will break up into groups and lock lips, also their black turns to a
strange green color. Not all of the barbs do this, it seems to be the
smaller ones(males?). Is this breeding behavior? I know the fish are
probably too young, maybe just territorial behavior? It seems like if
the barbs aren't eating or looking for food, they are often engaged in
this behavior. They used to chase my angels, but now it's the other way
around, if the barbs get within 4 inches or so of the angels, the angels
bite them and chase them off, I'm glad that the angels aren't taking any
crap from the barbs now:-). The clown loach gets along with everyone. I
just want to know if this behavior means anything or if my barbs are
just ornery.

Josh