I don't think you can get too vivid with fall colors! Example shown is common where I live and generates attraction for annual travelers and income for their hosts, just to see the colors!
This is a little more complicated, and I haven't tried it yet.
Can you ...add an object like tree1
Assign your color variation with Power Fractals here.
Save the tree as a new tgo
Then make a population with this new tgo
New population has rotation enabled
What I have trouble with is the scale of the power fractal when doing this in a population. It seems rather hit and miss at times.
I think you are on the right track with your experiments. Not bad choices for colors.
Thanks for the clip WASasquatch, I will check this out too!