how can i fit a light fitting?

i have tried to install a light fitting and i have 3 red wires ,3 green and yellow wires, 2 black wires, 1 blue and 1 yellow, could someone please help me as i am unsure where the wires go . everytime i put the wires in i seem to manage to get the light on when the switch is in the off position. i also know that some of the wires loop into another light fitting in another room many thanks sue.