To create simple loops, I typically just cut and paste groups of keyframes.
But for a more versatile solution, you can use the LoopIn and/or LoopOut expressions.
hmm tried that, it gave me an error.
any one else that know how this can be done? I get this error that says loop is not supported for custom properties.
Create two key frames say at 01:00 and 02:00. Now copy the two key frames and paste at 02:01. Now you will have four key frames with one loop.
In Effects Control panel, Alt click on Channle range(if you are animating Master Hue), Click on the small arrow button to open Expression Language. Go to Property and choose
loopOut(type="cycle", numKeyframes=0): .
This will create a loop animation of your two key frames.
Use the Colorama effect with the default spectrum and anmiate the phase and cycle values. Will require two simple keyframes at the start and end of the comp without any further ado....