[jxdxbx]

If something appears blue, it is blue. That’s all color is.

Also, if you took a sufficiently large quantity of air and put it into empty space and shined very bright white through it, it would experience rayleigh scattering—-meaning that air, when you have enough of it and shine a bright enough light through it, is blue.

[yawpitch]

By that logic the sky is near-Planck length ultraviolet, because if I put a sufficiently large quantity of it immediately beside a supernova it goes way past blue.

Color is a property something has under certain conditions, it is not a property of what that something is under all conditions.