Apologies Richard, I had just picked up your request relative to indicator issues, in the active thread section and had not read the whole thread...Duh..! Whether the same wiring codes are still used as they once were I have no idea, though I guess if you are looking at the indicator wiring you may be able to confirm the colour coding in use, if any.
As for diodes if seeking a simple explanation on how they operate as ever the interweb is your friend..
https://www.youtube.com/watch?v=6lep5e3KMdYGood luck.
