I am about to replace a ceiling light that must be earthed. The wiring coming from the ceiling is 3wires, 2 black & 1 that looks yellow but could be white. The wires exit from metal conduit. With the light that i just removed the earth was not connected but I think it should have been. The ceiling wiring had the two black wires going together to the blue neutral on the light, and the yellow wire going to the brown live wire on the light. How do I earth the new light? was the old light safe?. The wiring from the switch by the way is 2 red wires and an green/yellow earth..Please help I am confused.