RPM counter wiring

Hi trying to fit a new ecu to mk1, need to know what colours would be the RPM counter 12v supply wire and RPM counter signal wire? To get ecu RPM to work.

Anyone any ideas, I'm looking through the Haynes and can only see a black/red wire?

Any help?

a ecu im lost mate aftermarket or standard ?

takes feed from - on coil

Aftermarket, using original gauges.
Think I've worked it out now, Red/Black goes to gauge (guessing signal?), and theres a red which is the only wire which is giving any power into the 2 plugs into the back of the clocks.
Anyone know? Just to confirm this before I get my soldering iron out!!! 8O