Years ago, Adnan Merchant, who was on the autox Healeys list at the time, made a CAD drawing of the BJ8 electrical diagram (Phase 2, dual indicator light) from the workshop manual, color coding each circuit. It included a color key. This was fine, but still was hard to read for me with all of the circuits on the same page.
For my own purposes, I took his drawing and made multiple black & white copies of it on 11 x 17 sheets, then made my own color-coded separate drawing for each circuit. I used colored pencils to trace out the circuit for brake lights, fuel gauge, turn signals, etc. on a separate sheet (16 pages in all) and put them into a "Wiring" notebook. I have found it to be a quick way to troubleshoot a circuit when a problem appears. I keep the wiring notebook in the boot so it's handy on the road if needed.