Thought id figured this out, however i have no dash lights now. Did before....... but i now have hazards switch working ! im guessing i have some bad connections in there somewhere. ill keep at it and hopefully everything will work ( i know wishful thinking for a T25)
it's not just the handbrake light it also gives low fluid level indication (if you have a level sender cap and the wiring to the fluid reservoir) and footbrake dual circuit failure warning too.
A quick look at Bentley says your grey/green is the handbrake, you can easily check that at the switch under the handbrake
brown blue is level sender
How many pins has your edge connector on the module in the dash ?
It would be good if you change the title of this thread to something like 1983 wiring for brake warning light and maybe someone with an early van could take a look at theirs and give you the correct information, I only have late Syncro vans to hand and tbh the wiring diagrams for the early vans aren't that good in Bentley
Generic colours are -
Red - Battery Live (30)
Black - Ignition Live (15)
Brown - Ground / Chassis (31)
Grey / Green - Handbrake (HB)
Blue / Brown - Brake Fluid (FL)
Assuming you have the correct warning light as there are multiple versions
3 pin and 5 pin...
(some 5 pins are for seat belt warnings on the Golf mk1 etc) in which case you may see a terminal marked 61.
1983 Tin Top with a poorly DF and 4 speed DT box.
1987 Electrics and a DJ engine.
Maybe one day I might get it finished