Rule R18 A states:
No other sources of electrical power are permitted, unless used as part of a non-functional decoration per [R12e].
this allows you to power LED lights using a battery pack, there is no reason to power them off the cortex using illegal methods
I think it’s important to note that OP is already aware of this. I think OP is wanting to make it such that their LED’s RGB values can be controlled individually mid-match. It was noted before that this was legal in previous seasons. But now, thanks to the GDC it is uncertain if they are legal this season. Even though I do acknowledge the GDC’s organization of the game manual is nicer than it was 3-4 years ago, it is sad that the GDC recently has been making petty decisions that simply makes VEX feel and look more boring.
At worlds, @Grant_Cox told me to email him to “work something out” regarding lights legality, and then has proceeded to ignore all of my emails regarding the subject.
My robot had MC29 powered lights all last season, and nobody cared. I was prepared to remove them if anyone complained. Use them at your own risk.