This is apparently a stupid question, since many have successfully built their units without, as far as I can tell, anyone having ever asked it.
The instructions for 2.5* advise you to label the new waterproofed wires to the motors (I, II, III) since it is hard to tell one from another once the blue heatshrink is on. The wiring diagram for the DB-25 connector refers to them as A, B, and C. What I'm not clear on is which one is A and which is C -- it seems to me there are potentially two different places to start. I was looking at the motor from the top, resting on its mount, so I marked the wire replacing black as A, blue as B, and red as C. Is that right, or is it reversed?
*I cross-checked against 2.6 and it omits this instruction entirely -- whether purposely or not was not clear.