Going by this picture, look at the lower right corner where it says RX. See the S + -? That stands for Signal, Positive, Negative. Signal is white or yellow (depends on the cable you have), Positive is red, Negative is black. Put it on the connector in that order (white to the left). As long as both ends are in the same order (black, red, white) it doesn't matter which end goes to the Rx or ESC.