I have non a/c blazer and have the relay. Green is for temp to side of block on mine...that's the one I can trace. The brown from reading is likely the TCS(transmission control spark) and the other I am unsure of, maybe for electric choke?
There is a separate green wire in the same area for the temp gauge. The green wire connected to the relay was unconnected. I'm thinking you are right about it being for TCS. Either way, it's gone now and so are all the wires for it.
I decided to pull the entire cab wiring harness so that I could work on a table instead of around the steering column and honestly I was surprised at just how small it is. I guess I shouldn't be but I was.
Anyway, one of the changes I plan on making while I'm at this is to run the ACC circuit through a relay instead of having everything power through the ignition switch. I pulled the switch to take a look and decide exactly which wires do what.
connections in case it isn't visible: clockwise from the top, IGN, SOL, ACC, BATT, BATT, G2, G1.
At first I was confused by IGN and ACC but after some playing with the switch it made sense. According to the wiring diagrams, IGN runs to the fuel gauge, solenoid, and coil. It comes on when you turn the key on, just like ACC, but when you turn it all the way to start the switch cuts power to ACC, but not IGN. Conversely, when you turn the key to ACC the IGN circuit is not powered.
I plan on running the IGN circuit through a relay on my new fuse block and possibly ACC too.
BATT and SOL are obvious, power in and power out to the solenoid. G2 connects to the brake light warning switch (on the MC) and G1 is supposed to connect to the engine temp switch, but my truck doesn't have a connection here. I'm not sure what the point of this connection is though. I believe the brake light warning switch provides a ground when the light is supposed to be on but I can't tell how the G2 pin interacts with the circuit. Anybody know?
Of course all of this was a distraction from what I was supposed to be doing which is move the battery over to the drivers side. My plan was to pull out the stock battery tray, swap the sides around and bolt it back in. The core support is roughly the same on both sides, just swapped left to right, so it probably would have worked ok... except for the fan bracket I put there a couple of years ago.
That nice aluminum bracket blocks where it would want to bolt up, so I guess I'm building my own tray from scratch now.
At some point in the past my truck was converted from points to HEI so some of the wires aren't where they are supposed to be. For instance, the IGN wire that was supposed to go to the starter solenoid wasn't connected. I guess it wasn't needed?
Also, at first I thought the HEI coil was connected wrong but I was able to find where it plugged into the fuse block and it was indeed running off of the IGN circuit.
Since I am planning on trying to add cruise control 
I'll wire that into the brake light switch.
