Unless parked in a damp area... tends to get mildewy/mossy and
green-ish. If let go for a long time, especially on older finishes, it
can be very difficult if possible to get it back to normal.
I suspect that white is the longest lasting due to rejecting the most UV
rays. The darker the color, the more UV is absorbed. I have a 2005
Hyundai Elantra wagon in black, that lived in Arizona until 2016. Not a
speck of rust underneath, but the paint was totally baked.