If anyone raises an electrical query on the Citroen Specials forum the first reply is always "it's the green wire" as Citroen largely used one colour...
Peugeot wiring used to change colours when it passed through the bulkhead! That and the wires were identified by numbers printed on them so small you needed a powerful magnifying glass to decipher them.
The wiring itself was strange in that it used to suffer from oxidisation which result in a black deposit on the wires which resulted in much scraping with a razor blade to get it clean enough to solder.
To get back to the original post, on my 1971, you can't sound the horn if the headlights are on main beam! Not sure what, need to investigate!
Arwyn