Which set of wires are you talking about?

Are you talking about the set of three wires running directly to the motor?

If so, no matter how you connect them, the motor will work. However if the motor runs backward, just interchange ANY two of the three wires to reverse it's direction.

If you are talking about the wires from the ESC to the receiver, these must ALWAYS be wired so that the respective colors match.

e.g.

orange to orange ( signal wire ).
red to red ( positive voltage )
black to black ( negative / ground ).