In terms of warm or cold, my suggestion is to go warm for games with yellows, oranges, and reds and cold for games with greens, blues, or purples. I try to stick with one color for true GI, but if the bulbs are more to illuminate plastics to illuminate, don't be afraid to mix and match.
Quoted from Timerider:
Even on skin tones?? I gave up trying to LED my Bally Eight Ball. Every brand/color I tried made Fonzie & Pinky look either yellow/jaundice, or death-blue clammy. I've stuck with incandescent in most of my backboxes (and PF GI), with sparingly highlights.
Did you use Comet? I had that issue with the warm whites from Pinball Life, but I'm much happier with the bulbs from Comet.
PS: Comet for LEDs, Pinball Life for everything else.