To complete the simplest is to place one torch on a plinth so it is balanced on the plinth with the torch still in. Move the torch to its own color then pop the other in its color.
OK lift one of the torches say green out of the blue hole but it dosnt matter which.
Place it on the edge of the blue plinth so it balances then get the blue torch and put it in the blue hole.
Pick up the balanceing green torch and place it in the green hole.