It is indeed an orange and a white wire for this circuit.
So you found 12 volts on the fuse but not at the switch. Be aware there are two different fuses labelled "Brakes" and "Stop / Hazard". To complicate matters even more, no connector terminals are shown so I can not find good test points for you.
The "Brake" fuse should only have 12 volts when the ignition switch is in the "run" position. That is for the Anti-lock Brake Controller and is not related to the brake lights. Double-check the voltage on both sides of the "stop / hazard" fuse. Next the orange wire leaves the fuse box, then four wires are sliced onto that one wire. Those feed the brake light switch, the "RWAL" module, if you have rear-wheel anti-lock brakes, the hazard switch, and the audio alarm module. I can not tell from the diagram which side of the firewall that splice is on, but we can figure it out. It is pretty likely if there is a corroded connection in the firewall connector, it is going to involve just one terminal, not four individual circuits. Therefore, If the hazard flashers also do not work, it suggests the splice is inside the truck cab and the one bad terminal makes all four circuits dead. If the hazard flashers DO work, the break in the brake light circuit has to be on its own circuit, meaning four separate wires go through the firewall connector and the splice is under the hood.
If you can find the hazard flasher, you can check on its orange wire for 12 volts. If you do not know where it is, that voltage should also be on the brown wire at the turn signal switch. There are two flashers. The turn signal flasher has three wires. The hazard flasher has only two wires. See how far you get with those voltage measurements.
Saturday, September 17th, 2016 AT 1:07 PM