George,
You can't always rely on the colour codes of wires. BUT If you had a vehicle that was supplied to the US of A then you'd have a fighting chance of finding the wiring diagram on
www.startekinfo.com
As it is you have an engine that is similar to those used in a W201 so perhaps those wiring diagrams will help.
Have a look if you want to...
...I reckon, however, (as said before) the fastest way of working out what the wire does and what it is for is to trace it back to the ECU plug. Just do a simple continuity test and tell us which pin number it is. From the information in the W201 FSM there are (perhaps) three different ECU plug types so we can narrow it down to a few possible components.