Hi,
Just saw [this][1] tutorial.
You can just make a “Random Unit Vector”, then convert it to LinearColor, and just set your light’s color with the obtained LinearColor.
As described in the tutorial, you can set a timer to choose how often you want the color to be changed.
Hope it helps.
EDIT:
Added a simple screenshot of the timer-based Blueprint, that can be found on the tutorial as well.
