Does air have color? Is it relative? Things will perceive at least slight variations in that property of something. It would depend on the intrinsic property(ies) of the thing in question. Air is mostly stuff small enough to not be as bound by the Earth as much as stuff at least slightly more massive than the components in question. When there's no air, there's the sacred black. Look in space, or on the moon. Different places could have differently hued atmospheres based off what the air is made out of on that world.
At night there's no blue in the sky because there's no main light source for reflection; the sky is probably different colors at different times of the day, if that has anything to do with the quality of the air.
Unless you want to take a bunch of air and look at it up close, it might be possible to distinguish some characteristics, such as 'oh look, this one looks kind of green'.
Can't help but want to bring light into the thing. It seems just based off the visible band.. How complete does one wish to be? Would the color of something depend upon its temperature and the energy it exudes? Apparently that's a thing... Air and most room temp things can be kind of colorless in a sense but if the properties were altered in a manner quasi observable shifts in hue can probably be "measured".. There might have to be a base color of sorts but what we see could have a color we aren't accustomed to since it's our main gateway to regular energy conserving access to some external idea of what things are
jeez, how half assed. i don't know what the hell i was doing.. shoulda been studying for this exam i have to go to in 5 minutes
I'd like to know more about the respiration process and how it allows activation of potentials?