One of the reds is a mains spur (Perm. Live) Test it with a mains tester.
The other red is the live feed to the switch. Both of the reds go into one terminal.
The black with a red sleeve is the return switched live wire which goes to the live feed for your lamp.
The black wire is the neutral for your lamp.
The green/yellow is the earth which must be connected to the lamp if it has metal fittings.
Cledlyn
September 2008