FWIW: I suppose it was the little cold spell here (after a brutal summer it is very welcome) in PA to get my interest in the Polar Express revived...so I followed up with customer service today at lunch break...the person didn't have any updates on the RPO color solution(s), but took my number and said he'll look into it.
I think we're going on a decent lapse of time since the issue was first brought to Lionel's attention. Given the global pandemic, its likely some things got sidelined. Nevertheless, I recommend others giving them a call.
I still have my RPO cars (white and black roofed) sitting in boxes waiting for either re-paint or shell replacement. Given that they're scale cars and relative high price point, I am expecting a satisfactory resolution.