Woodland First what came to my mind was bright colors. Don't go pastel that is too much. Just clear, strong (not so strong that they blow your eyes to smithereens) colors. They should enhance the upbeat nature of the game. Racing world is always colored with clear colors; yellow, red, white, black, green, blue etc. I don't remember seeing broken colors (especially shades of brown).
If you look into the color world of Crash Team Racing, Mario Kart, Candy Crush, Puzzle Pirates etc etc. It is all clear colors. Look into that would be my initial suggestions. Oh! Think LEGO