There was a post a couple years ago where someone was checking out the then new High Country models and had his tire thermometer with him. IIRC it was a 60 degree day in December and he noted a 6 degree INTERIOR wall temperature difference between the grey High Country and a similar white FW sitting next to it. Something like 10-12 degrees on the exterior. Coming from AZ, even in the winter, full sun can get uncomfortably hot. I sure as heck wouldn't want to buy a new FW then turn around have have to paint it because I can't get a white, or very light, exterior.
I don't know how it relates to paint or interior temperatures, but with a hot sun I can keep my hand on the white part but the dark decals will burn your hand quickly.