Heater box cables.

69 Dart, no A/C.
I have 3 control cables from the control panel to the heater box. 2 are marked yellow and are the same length. 1 is marked red and is longer than the other 2 yellow ones. The service manual says nothing about what cables attach to where. Anyone help me out here? How do they connect to the control panel, and how do they connect to the heater box??

Thanks guys.

George