Found this info on it
Throughout the show, Colt drives a 2-tone brown GMC Sierra Classic 1500 4X4 made in 1984 (you can tell this by the headlight design...2 rectangular lights on-top of each other on left and right side). However, the year, as well as the model, of the truck are ever changing (you can tell this because the headlights are sometimes singular large round lights on each side which says it's between an 1980-83 truck). You can notice this in the opening credits when the truck jumps through the glass.
They even have toys of it
