I did the exact same thing this weekend and installed the Acewell 2856 on my 81 r65. I followed the labelling in the image below which shows the colouring, but mine was slightly different. The thread you need is this one:
http://www.advrider.com/forums/showthread.php?t=527749Rev Counter (Black?) to Acewell Yellow
The yellow is the cable which you run around the one of the black HT coil wires.Oil Light (Brown/Green?) to Acewell Grey
Same on mineNeutral Light (Brown/Black?) to Acewell Purple
Same on mineSwitched Live (Green/Blue?) to Acewell Red
This was green on mine from the ignitionHigh Beam (White?) to Acewell Light Green
Same as mineEarth (I'm pretty happy that this is brown) to Acewell Black
Same as mineUnswitched Live (this can come from the spare terminal on the ignition switch?) to Acewell Brown
I used the red cable on the auxillary socket and then switched it to the red from the ignitionCharge Light. I have a separate bulb light for this which requires 2 connections (Blue and Green/Blue?)
This is the same on mine
I have the model without the gen light and a sidelight indicator which I hooked up to the grey/black.
All worked first time and then every time I tested it thereafter