Are 'arduino 1' and 'arduino 2' just two pins on the same Arduino?
Is the "-5V" really MINUS five volts? If so, why?
Why not just connect the LED directly to two data pins:
Pin2 ----- Resistor----- LED----Pin3
Then you will get one color with Pin2 HIGH and Pin3 LOW and the other color with Pin2 LOW and Pin3 HIGH.