Some cars are hard to tell. Go to GT auto, paint it, and if you don't like it, then quit the game from there... it will not save that you've painted the car.
If memory serves me correctly you will lose those stripes, best to keep it as it is, as it's pretty uncommon to see that livery on the AC anyway. I got mine from grinding a ticket, took absolutely ages!
Even if you could keep the stripes you wouldn't be able to paint the stripes anyway. I tried to paint the '10 camaro thinking it would be one solid color but different color stripes matching the car would come up.
Also noisiaturismo I have a spare I could trade, I'm only interested in a car painted with the new DLC paint. If you bought the DLC let me know, and we can work out a trade.