i have to agree with chisuu, the color pallate you used is very weird. the best way to figure out what a good color combo to use is to just google a race car of the base color you want (in your case, green) and see what supporting colors others use in real life.
that color of green you used seems to always either be used with black, or other pastels, yellow and blue. but the edges are always rounded, so you may want to reconsider your pallate alltogether.
also the text on teh side isnt that great. make it smaller and bold it, remove the "Driver:" and just put a tiny little flag (your country, obviously) and tuck it right up underneath the side window and itll look a lot nicer.
also learn to paint over multiple peices of the templates. all you seem to have done is put orange and green boxes all ove the skin so the colors suddenly end/change