I agree, the colors look better than white. But, with the walls held together with adhesive, most adhesives melt at a certain point. If an adhesive was chosen for the white walls, and it holds to a certain point, that point can be exceeded by a darker color. Then, delamination.
Whether you paint it, or put decals on, it could absorb much more heat than white paint. Not good, if it gets hot enough to melt the adhesive. If you always camp where cool, no problem. But, most of us will be where it is hot, at some point. Not necessarily intentionally, but we may have to go to Texas or Florida for some reason.
