[Mr. Lim]

int redLight = 0;
int whiteLight = 0;

void updateLights()
{
	int combinedLights;

	combinedLights = (redLight << 1) + whiteLight;

	switch (combinedLights)
	{
		case 0:
			myRelay.set(Relay.Value.kOff); // M+ and M- = 0V (Both Off)
		break;

		case 1:
			myRelay.set(Relay.Value.kForward); // M+ = 12V, M- = 0V (White Only)
		break;

		case 2:
			myRelay.set(Relay.Value.kReverse); // M+ = 0V, M- = 12V (Red Only)
		break;

		case 3:
			myRelay.set(Relay.Value.kOn); // M+ = 12V, M- = 12V (Both On)
		break;
	}

}

Something like the above will give you two independent variables representing the lights that you can change without knowing the state of the other light. Just call updateLights periodically.