I've traced out the cable that goes to the tool head on the Geeetech A10 Pro with GT2560 V4.0 board.

                     O X Heater-
                +24V X X +24V
                     O O
      Cold side fan- X X Cold side fan-
         Thermistor+ X X Thermistor+
BLTouch Brn, Blk (GND) X O
           BLTouch R X O
           BLTouch Y X X BLTouch Wh
          Parts fan- X O

Xs are filled, Os are empty.
The fans and heater cartridge are tied to the +24V side, switched on the negative side.
BLTouch wires are Brn for Brown, R for Red, Y for Yellow, Wh for White and Blk for Black.
The thermistor provides a resistance value to GND. At around room temperature it's 110-120 kilo-ohms.

I'm overhauling my own printer, and mapping this cable out is part of that project. I hope this is helpful to anyone out there looking to replace the board in their Geeetech printer. If you'd like to know more about my own project, check the Ship of Theseus tag.

Alright, so back in 2020 I got a Geeetech A10 Pro, a respectable Ender 3 clone that even did some engineering things better than the Ender 3 that was out at the time. Thing is, it's really showing its age.