With the jumpers removed from the input side of the crossover box, you'll connect one speaker pair to the "low" input, and the other pair to the "high" input. And yes, red would be positive, as long as the other end of the red lead is connected to the positive side of your amp's output.
Here's what the manual says:
Bi-wiring requires two sets of speaker cables. They may be identical or one set may be specialized for high frequencies and the other specialized for low frequencies.
A. Remove both jumpers on the crossover box.
B. Connect one set of cables to the low cable input and the other set to the high cable input. Connect the other end of the cables together (observe +/- polarity), and connect to one channel of the amplifier outputs. If frequency specialized cables are used, connect them to their respective inputs. In either case, the other ends are connected to the same amplifier channel.
C. Repeat same procedure for the other channel.
Here's what the manual says:
Bi-wiring requires two sets of speaker cables. They may be identical or one set may be specialized for high frequencies and the other specialized for low frequencies.
A. Remove both jumpers on the crossover box.
B. Connect one set of cables to the low cable input and the other set to the high cable input. Connect the other end of the cables together (observe +/- polarity), and connect to one channel of the amplifier outputs. If frequency specialized cables are used, connect them to their respective inputs. In either case, the other ends are connected to the same amplifier channel.
C. Repeat same procedure for the other channel.