How important is the look of a car to you?
Scrap yard?
Have your son varnish the parts which don't have the right colour.
That should keep him busy for a while (I did two doors once and I would never do it again )

Actually I think that would be a fair deal between you and your son. You might even help him a bit = bonding.
Sorry, you were taking the attention off the "feeling-bit".