In that case you need to know which switch operates it from the other end, take it off the wall, and look to see what wire goes into the common terminal, on the switch you have it will be the top one, if it is a yellow wire for instance then the yellow one in the other switch must go into the common,then you would connect the two red wires together and place in one of the other terminals, then put the blue wire with the black wire and put in the other terminal, the green and yellow is the earth that goes onto the metal box, or terminal inside the plastic pattress, Please be very careful, Turn off all the power, make sure all the bare wire goes right into the terminal and tighten properly. If you are in any doubt at all Please do not attempt to do this job and consult a local sparky he will only charge you a few pound to connect the switch and you can rest assured it is done 100% safely, I am only giving this advice so that you can connect it properly, but please take care.