Hi,
I am connecting a new light. There are 2 cables coming out of the ceiling; 1 cable has 1 red and 1 white wire. The other cable has 1, red, 1 black and 1 green / yellow.

The cable with the red and white is from the switch, (I think). The other is the mains for the light. The light itself only has 3 connections (red, black , green); i.e. no room for the white. So when I connected, leaving out the white, the light stays on and cannot be switched off.

What shall I do?

Are u in USA?

Not use to the color code u gave.

Attach one wire from switch to one wire from other cable.

Attach other wire from switch to black wire for light.

Attach the 2 green together.

Attach the remaining 2 wires together.

If u have a multimeter, u can test to see which is hot and which is neutral with meter set on AC volts. Set on ohms to test if red/white cable is the switch leg.

Chuck