I suspect you would not see any effect in the hot room scenario because the photons carrying the image to your eye pass completely through a homogeneous substance in both cases. I believe it’s the density differences at the boundary, with that boundary intersecting the complete image that causes the effect. I think the way to think about it is on a photon level, source destination, frequency, gulp and burp theory, and dissipation. The sky is blue because the atmosphere dissipates the other frequencies more readily therefore the blue frequency photons reach your eye in greater concentrations. The sun is actually green, but we don’t perceive it that way on earth.