Those are builder access wires, stock, put there by Ford. You will find the other end of them under your dash near the fuse panel. All they are is a built-in through-firewall wire run. Guys use them to hook up gauges, lights, anything that needs a wire through the firewall. But, here's the nice part. Under the dash, you will also find two more wires. They will have a molded cap on the end. These wires are power sources, one constant 12V, the other is a key-on source. You'll notice they aren't the biggest wires, so if you do use them for anything more than a few lights you'll want to use them to trigger a relay and run a larger gauge wire from the battery.
'02 F-350 "Babe The Big Blue Truck" 4x4, Ext. Cab, 8' bed, SRW
DP-Tuner 80T, 160cc single shots, GTP38R turbo, Ceramic coated IH up-pipes, coolant filter, 6637, DIY exhaust brake, openair CCV, propane, SBC DD all ceramic clutch, ISSPRO EV boost/pyro/HPOP pres./rear end temp, 4" lift, traction bars, 255/70R22.5 tires, York air compressor, 16 flashy lights, 12 strobes, 12 switches on console, 9 switches on the dash, 7 two-way radios, 5 air horns, laptop, siren, 105 gal. in-bed fuel tank, Kennesaw Mountain front bumper
'86 H-D Sportster - 16" apes, custom paint, custom pipes to fishtails, single fire ignition, leather saddle bags on custom brackets, bagger fender, solo seat, home made luggage rack, all LED rear lights
'66 Bronco "Big Little Monster"