Well... value is subjective. Strict preservationists won't like any changes but these are a small minority of pinballers.
Generally, if a lighting mod is professionally done "in the spirit of the original", it won't affect the value much either way. I've added extra lights to the backbox, added stealth LED's, all of my games get the cabaret light treatment around the top arch, etc... no one ever notices. If they do, they never mention it. *shrug*
Funny fact: Surf Side won best runner-up "original condition" machine at TPF in 2015 and it already had the cabaret lights installed. D'oh!
I'm not a fan of the whole crazy rainbow-changing, super bright, too-cold-white, unbalanced color matching LED thing. I'm pretty sure that kind of thing turns most people off, but hey, at least it's reversible if using drop-in replacements.