Generic input and output colours

I'm developing a game which features various power creating devices, machines that require power and cables to link the two together. Because of a bug that caused the cables to drag power from the all the cables around it (meaning if arranged in a row they showed power readings exceeding what they could possibly have), I have decided that each cable will have an output face and three input faces. I would like to colour code these faces so the player can easily tell the difference between the output and input faces. Is there some sort of standard colours for these? I don't mind (and will probably have to) include some sort of tutorial explaining which colour corresponds to what, though if there is a standard I would like to stick to it.