I kept my all male hap tank at 77-78F year round. Colors were always great, but no guarantee on aggression issues. With large sexually adult males sometimes things can go sideways, even in a large tank.
Temp will tamper with behavior and mobility but lighting will be the factor for color. Too bright or too dark and their color will fade. If their color is not so bright, tin foil a section of your light and tone it down. But as stated from others, I keep mine at 77-78