what colour the rev trigger wire is?

[Sy-superfly]

Ive just replaced the clocks for a rev counter only, but I don't know what colour the trigger wire off the front coil is? If you know this you might also know what the live and negative is.

Thank you

[Sy-superfly]

Forgot to say it's a carby 2000 model

[hardhat_harry]

Seem to recall its black and yellow.