Get an "S" rank on three races with the same truck to unlock its alternate paint color. Alternately, win ten races with a single truck to unlock its alternate paint color.
Complete the indicated task to unlock the corresponding truck. Note: The total number of stars you currently have is not tracked by the game and must be manually recorded.
Unlock Super Excite Mode then get passing ranks in every race in the Bronze, Silver, Gold, and Platinum Cups to unlock the Diamond Cup with the Crystal Road track.