The Red is alway centerpin so if you line just red up then you can still plug backwards.

Your set up is indeed black to brown as Jimmy indicated and it will allways be correct if you observe that.

Actually the Hitec S, the Airtronics Z and the JR Plug which are all compatable are keyed mechanically to plug only the proper direction with two edges of the plug with a very small champher edge as does the female plug. But they can be forced backward with only a little more effort.

John