Hey Ken:
The connectors are more or less standardized these days, at least for "full sized" radios. There's two, JR and Futaba. The Hobbyking receiver uses the Futaba standard, so if you use a servo with a Futaba-standard connector it'll plug in and it'll enforce polarity.
However, just to confuse things, you can plug a JR-standard plug into the thing just fine -- but you can plug it in backwards as easily as forwards. If you squint, you'll see that the receiver shows the proper polarity, so you can go ahead and use a JR-connected servo. Fortunately, the wires are arranged so that if you do plug one in backwards, the worst that'll happen is that it won't work but nothing is damaged. So you can try it one way, and then reverse it.
Color-coding is sort of universal -- black is always negative (-), red is always positive (+), and signal (s) is always some other color (usually brown or white, but you see just about anything).