Would depend a lot on your style of music and as noted previously, personal preferences. The old Color Toolbar was a great utility that I believe Lukas is going to incorporate into a new feature in one of his add-ons that will aid in automating the process.
But just to share, I personally use
RIGBY (
Red,
Indigo (actually dark purple in my preference),
Green,
Blue,
Yellow) as my colour organization "system" for "conventional" (Rock/Pop/Folk/Country) styles.
Red - Drums - Acoustic drums, percussion and electronic drums each get their own bus out to a main drum bus. Slight colour variations for each type of bus, but they're all red
Indigo - Bass. I use just a single bass bus for synth, acoustic and electric basses
Green - Guitar. As for drums, different busses and colour shades for electric and acoustic.
Blue - Keys. Pianos, Organs, Synths. I usually have a lighter blue shade for a separate "Strings" bus and instruments that all get routed with keys (I don't do any orchestral work obviously).
Yellow - Vocals. Again separate bus and shade for background versus lead vocal to a main Vocal bus
All main instrument buses go out to an Instrument Bus (pale pink for visual identification)
FX channels are generally whites and greys
Instrument bus, FX Channels and Vocal bus goes out to a Mix Bus (also a pale pink shade), which then goes out to the Main (Grey). Listen bus is also grey.
IIRC, Joe Gilder uses a Blue, Red, Green, Brown, Yellow colour scheme for Drum, Bass, Guitars, Keys and Vocals (same order, different colours). Once set up, it's really easy to incorporate as templates so standardization from project to project becomes incredibly easy. That I think is the real benefit of thinking through your choices and sticking with something that works for you. (Not advocating, just keeping the conversation going

)