wire harness

do you just match the colors or do they have a code......because i got a harness for the dash but the harness wont fit the back of my cd player....so do i connect the wires or what????? IM ALL CONFUSED

First I need to know what year truck, what harness you are talking about and if you are adapting an aftermarket radio or using another factory one

Depending on your year of the truck go to wal-mart or any other store (recomending wal-mart) if you go there buy the harness for your ford ex and then connect the harness's if that dosen't work return one and just cut and connect the wires and vuala (how ever you spell it)