Backup wiring

The backup wiring is two orange wires from the switch to the bulkhead connector on the engine harness. Then it is a blue (or purple) wire and white wire on the under dash harness; however, those two wires are separate from the main harness. The blue/purple wire matches up with a purple wire on the rear harness connector. The white wire connects to the wiper switch on the dash. Is that just for ground?