4 ms·Air is mostly nitrogen. Nitrogen gas is blue. There.by alejohausner 8mo agoAir is mostly nitrogen. Nitrogen gas is blue. There.pbhjpbhj 8mo agoGo watch a video of nitrogen gas evaporating from liquid nitrogen ... tell me what colour you see?mjanx123 8mo agoOxygen is blue actually. That only contributes to the sky blueness a little tho.