As an addendum to my statement, the three wires on a servo are +, -, and SIGNAL. It will be easy to see which is which if you have a receiver battery pack. The + and - are common on all servos and battery sockets, so however the battery pack plug is configured tells you which is which on the servo. If you have to switch a wire or two around, you can poke a pin onto the tab of the terminal to pull it out of the plastic socket. Swap 'em around nice and neat. If you can't do that for some reason, you can always cut wires too, but only if you are going to solder them. Dont just twitch them together, thats just asking for trouble!
Or of course, you could just make sure you get a receiver compatible with your brand
