Heat comes from the Far-IR spectrum, so you only need something that is...
1: IR reflective
2: Not Heat-conductive itself (an insulator)
The color of paint is irrelevant. Black paint can be IR reflective and White paint can be IR absorbing...
There is no singular "element" or "compound", which is capable of doing this. Ceramic is the closest you will get.
That rules-out aluminum, because, though it does reflect heat, it also conducts heat, so it "reflects", both ways, inward and outward. (Think of a tin-foil/aluminum-foil wrapped potato, and now you have every single car ever manufactured with metal.) Vehicles are not made of pure aluminum, they are an alloy, as is tinfoil. Magnesium is a large part of aluminum used for adding rigidity to it. Magnesium does not reflect heat, it absorbs it. (Magnesium is what you use to create fires, with striking wands.)
Ceramic is highly IR reflective, by conduction-rejection, if manufactured correctly... However, unless it is solid ceramic, it is almost as useless as aluminum to reflect heat. (The conduction of the "medium" used to bind/contain the ceramic, {paint}, will simply transfer heat in both directions, using the ceramic to act like aluminum, reflecting it both inside and out, whatever it absorbed.)
This is why foil-masked (or surface-Mylar-masked), insulation is the best solution. It reflects with the pure-aluminum, but since it is thin, it transfers only a little conductive heat, and that is against a highly insulated surface of foam. Thus, it reflects the MOST outward, resisting the heat that would normally pass inward. (Same for internal generated heat, which includes your 98.6F-degree oven in your belly.)
I still don't understand the use of "glass insulation"... Last time I checked, glass was thermally conductive. Glass windows, glass cookware, glass test-tubes... Ceramic kilns are used to focus heat to melt glass, metals and to strip-away paints. It is a horrible insulator. Dead dry air is better.