Oh with you, couldnt tell you with these, but the Rotkeils change colour all over, the head goes a darker blue, the red on the shoulders on the male gets a deeper red and their anal fins go from yellowy orange to deep orange. The pair of Greens I had for a while, their anal fins changed colour before they spawned, well not changed colour, the colours became more vivid. The best way is the female will start shaking and shimmying at the male then start to clean off a rock or some wood 
