I think people are blowing up the paint not matching the vin issue a bit. The average buyer usually isn't too concerned about making sure the color matches the vin code.
If it was a "red flag," sure I'd ask questions, but I'd probably already have questions at that point. If the answer was as simple as "It was red, I decided I wanted it orange," that's pretty straight forward. If I really felt like the seller was hiding something, I'd probably be walking away well before asking about paint.
Now, if it was painted orange but still had red door jambs, trunk, and engine bay... that would just annoy the crap out of me.
DD: 2015 Toyota Tacoma TRD Sport
Lady's ride: 2016 VW Tiguan
Pride and Joy: 04 QSM/red M6 (1 of 344)
Retired for DD duties 3/23/15 at 120,600
Full JBA exhaust with shorties and catted mids, Griffin radiator, Lovell's Shocks, King HHD springs (1 inch drop front, 1/2 inch rear), various whiteline poly bushings, DSS 1 piece, Hyperblack 19" VMR VB3's, 05 hood, 05 bumper, Mavman color matched spoiler