For me, it completely depends on the year the game was released, and the theme of the game. The older the game, the harder it will be for me to have interest in using LEDs, except for insert fade (typically blue or green) and perhaps 1-2-3 lane plastics (red), and perhaps a few select spots.
I try to not use color if it will wash out the artwork.
RARELY a color LED behind a backglass. That's absurd. A total insult to the artist who made the art to use white light. (I tried LEDs for the TAXI stoplight top right, and it doesn't quite work, but a paper mod will fix that, to shield the color bleed)
A few examples from my collection:
1) Grand Lizard
outdoor jungle theme
1986 pin
LEDs belong in two few choice spots (the lizard eyes for brightness and contrast), but I want this to look and feel like the jungle. There ARE NO LEDS in the jungle, unless you are at a frickin' modern zoo. I put a cold white behind the sword in the backglass to create contrast from the warm glow of the 47's in the backglass. ALL 47s and 44s.
2) Space Station
outer space theme
1987 pin
In my opinion, when I think of a Space Station, I think of CLEAR COLD WHITE light. Is that accurate to outer space? I have no idea, never been there. I just think back to 2001 A Space Odyssey, and how I thought the space scenes were "cold" in feeling to me. The idea of CLEAR COLD WHITE light to me, means things should be VERY bright when possible, with hard shadows. So yes, I went with CT cold white frosted for the GI. To contrast the GI against the inserts (I think contrasts are important) I went with 44's in the inserts.
Backglass? I went cold white LEDs, BUT NOT in the ring. I went 47's in the ring. WHY? Because you can see through the plastic and I wanted the player to think he's looking up into all incandescents. I left the "Space Station" bulbs in 47's to contrast that warmth against the cold white station.
3) Diner
Indoor 1950's greasy fun restaurant theme
1990 pin
ALL incandescents. Nothing to think about here. LEDs have nothing to do with this theme. DINERS are shady, greasy, dirty, poorly lit places.
LIGHTING SHOULD MATCH THE THEME. There are no hard rules here. How the theme feels to you is subjective...
More to come later...
thanks.
-mof