The 2006 Colorado is a mid-size pick up truck available in Regular, Extended, or Crew Cab in either two or four-wheel-drive configurations. Trim levels range from the base WT (work truck), LS, LT1, LT2 and LT3. A 2.9Liter four-cylinder engine that produces 185HP is standard in the WT and LS models, with the optional 3.7Liter I5 that produces 242HP. The 3.7Liter is standard on the LT models. All models come standard with a five-speed transmission and with a four-speed automatic transmission as optional.