I just saw this.
I can not help you with the wire colors but I installed a Bartolini Preamp and Pickups in my L-250. I just could not get along with the stock electronics. Maybe I could had mine been a fretted bass but being fretless something had to change.
Got my bass mostly sorted wiring-wise. I couldn't get the series/parallel switch combo dialed, so it's series/kill switch. I use s/p on my fretted set-up, but can do w/o it on this fretless. It finally sounds as good as I always hoped it could/would.

I ended up not using the Bartolini's and re-installing the Wilkinson's MM style pu's. Proves there's a variety of ways one can achieve a personally desired tone.
To not cause confusion, this thread was in relation to a custom fretless w/an L-2000 electronics harness installed.
Also, I'm not 100% positive on this, but I've heard that G&L is being purchased by Fender. Anyone else hear this?