Idea is good. It's like arcade + match3 and i think it can be very addictive with good realisation.
Current realisation is poor. Rules are not clear and obvious. I didn't understand what to do before read description. So some in game tutorial must be created or short tutorial intro with rules description.
I suggest to create some car colour change indicator. So player can see what colour will be next.
Car colour must be more clear visible.
Anyway I think it's a good try for school project :)
Good luck.