Check the Controller and lights by selecting one of the fixed color modes. Reset the light(s): Hold the Controller button until it resets and switch back ON the device. Try again and see if lights remain in sync. If not replace the Controller.
How do I turn on my IntelliBrite pool lights?
https://www.youtube.com/watch?v=dugotHIW0tA
How do you know if a pool light is bad?
If the bulb tests well (3-20 ohms) the fixture is probably bad. Try a new bulb without closing the fixture. It probably will not light, and the fixture will have to be replaced. If the bulb tests poorly (overflow, open, no continuity, infinite ohms), the light most likely will work fine with a new bulb and gasket.
How do I change the color of my Pentair pool light?