The circuit board can be made in any color you like...almost any color. The actual circuit board is not green, but a printed material called solder mask. This is a layer of solder-resistant resin, the part printed on the pcb prototype circuit board that should not collect solder. This prevents the formation of solder bridges between the IC pins, and in the old age of wave soldering, it prevents the circuit board from picking up a large amount of unwanted solder. Green is a pigment in resin...