Not sure why the wire colors don't match. I remember doing a few Ranger Sports without any notable issues. The (+) Brake wire should be Purple/White. It is in a connector above the brake pedal at Pin 2. Here is a photo :
If there are no Purple/White wires in that plug, use your Digital Multi Meter to find the (+) Brake wire. You should get +12V when the brake pedal is depressed.
The R/S issue is due to the fact that your vehicle has the Ford PATS3 transponder based engine immobilizer system. You can verify this by wrapping the ignition keyhead (plastic area) in 5 or so layers of aluminum foil an then trying to start the engine with the key like normal. It shouldn't start and there should be some sort of "Security" light on the instrument cluster. You will need a bypass module to fix this R/S problem. There are 2 basic ways to go.
1. Get a "key in the box" style bypass module like the Directed 556UW. You would have to sacrifice a working key into the 556UW but if you currently had 2 factory unique working keys, you could purchase a transponder key blank off EBay, get it cut at any hardware store and then program it yourself to the truck. The 556UW goes for ~$11, the key is about $13 and getting the key cut is about $2.
2. Buy a bypass module like the Fortin EVO-Ride, EVO-Key, Key-Override-All, Directed PKALL The EVO-Ride can be found on EBay for $25, delivered. Figure $40 plus for the others. The bypass wiring is pretty easy and shown in the install guides.
Notes on bypass modules.
The "key in the box" bypass will require a working key, placed in the box and left hidden under the dash.
The "key in the box" bypass has an antenna ring that must be placed around the end of the ignition key cylinder under the steering column cover/shroud. Location is critical and very cold weather can impact performance.
You need two working keys to add more keys to the immobilizer system.
You need two working keys to add/program a data style bypass module (like the PKALL).
Data style bypass modules are very reliable, provide better vehicle security and are not affected by cold weather.
The Tach signal can be found at any F.I. It will be the non-common color wire ( compare several F.I.'s to ID the common color wire ). Then do the R/S Tach Learn process. Running in Tach Mode provides more consistent starts in cold weather. Bulldog Security seems to indicate that Brown/White is the common color. Another site indicates Violet is the common color.
Soldering is fun!