The Green wire is connected to the GND position. GND is the battery Negative.
The GND on the right side of the photo is connected to the GND on the left side.
The three colored wires come out of the right side of the board and go to the next board.
The Plus on the 12 volt battery is connected to the Red wire and to the "+12V" on all of the circuit boards. The "+12V" on each board is connected to the other "+12V" on the board.
The "IN Motor" and "OUT Motor" on each board are connected together.
The jumper on the left side of the board selects the Fahrenheit temperature that will cause the 2-Port Valve to open.
A Thermistor connects to the Center Connector.