have noticed with my spec Ampah that the males spar off frequently. They take the head-down stance and the dominant male gets very dark, but not breeding colors.
There are occasionaly displays from dominant females also, they more do a side by side stance with a nip here and there, and a dominant female has a litle better colors for a female. This is also true with the Parvulus but usually the dominant female gets close to having mating color just not as intense. With the Pavulus, the sub dominant male is very hard to tell from a female except the blue edging on his fins is more intense, but the lower half of his body does not turn dark, his anal fin slightly darkens. The dominant male Parvulus gets near breeding colors and flashes then chases the the sub-male to the back of the tank.