Well, I was curious to see what maroon cars might look like, so I applied Photoshop to a the following photo of a passenger train at Los Pinos. Personally, I prefer Pullman green, although in looking at this photo I could easily grow to like a dark maroon passenger consist.
In any event, more important that the color is that the passengers be well-maintained and clean (i.e., spotless!). They can and should look sharp whether they be Pullman green or maroon. I remember toward the end of GB's regime, the cars had really become unsightly. They did not look like something I would be proud to invite my friends to ride in.
I don't know what color paint lasts longest, but I did help paint two steel passenger cars last year, and I was told that they had last been painted three years prior. I was amazed at how bad they looked after three years.
If the image url doesn't work automatically, you can try this:
[www.binkie.net]
Curt