Heated objects glow the same colors no matter what they are made of

True only if light emissions aren't dominated by chemical effects or filtered by structural effects. Plenty of materials burn at different colors. Although if you wait out the chemical reactions and keep it heated, it does eventually end up with just blackbody radiation too 🤷

But corrected by emissivity factor. Emissivity factor is also not constant, and changes as both a function of material and temperature. Probably associated with band gap fluctuating wrt. Temperature

Unless it is a gray body. For somewhat accurate measurements you must do math.

Aluminium doesn't glow, even when molten though?

Which makes iron a suitable substitute for tungsten at 3000 C