I'm trying to replace old ceiling light with a new one. New light has only blue and red, no green. There are 2 cables coming from the ceiling each with 3 wires. Green/blue/red and green/black/red. I've blocked green/green and tried blue/black to blue and red/red to red but light goes on but not off. Blue to blue and black/red/red doesn't work. Any suggestions? UK.