Truck cap lighting question

I have an 03 Silverado that I just put a cap on, there are 2 wires that come down from the driver side neither are labels +/- where do i hook them to in my brake light on the driver side 3 wires go to the brake light, blue brown and black,

Also on the passenger side there is another single wire that comes down, i believe it's for the dome light what do i hook that to? None of my friends around have caps on there trucks so i cannot compare. Thanks in advance

Canopy installers just tap from the drivers side tail light for the canopy's brake light. I went a step further and added 2 clear lights for interrior lighting in the canopy. I also installed a plunger switch so when the rear canopy door is closed it shuts off the lights. I feed that from the trailer plug (Hot all the time) Plunger switch interrupts the ground.
Cheers