There are 3 places where one can find wiring diagrams for G&L instruments:

1. 1.The Basses by Leo (BbL) has a large collection of schematics focussed on basses. At the bottom of that page, one can even find some popular mods, notable the “K Circuit”.
   

2. 2.In a previous version of the G&L company website, a page was featured with a mix of guitar and bass schematics, now only accessible in archived form through the Wayback Machine.
   

3. 3.Beyond pictures of wiring harnesses of modern G&L instruments, the Gallery of the current Guitars by Leo website also has a number of schematics in the “Instruments Manuals and Wiring Schematics” album, included below for models where other sources are lacking.
   

Although the 3 sources feature G&L material, the schematics provided, even those by Paul Gagon, are not necessarily flawless. Please check the pictures provided in the “Wiring harnesses” section on this site. Esquire and Jerry Donahue wiring are included here for completeness.

Finally, here some resources to understand color coding and values of resistors and capacitors:

1. 1.Capacitor Markings section in the Wikipedia article on the capacitor.
   

2. 2.Alternative source on capacitor markings.
   

3. 3.Electronics Tutorials - Capacitor Colour Code.
   

4. 4.Electronics Tutorials - Resistor Colour Code.
   

5. 5.General Wikipedia article on electronic color coding.