The next most common is oxygen, at about 21%. Together, these two gases make up 99% of the air. In other words, these two gases make up almost all of the air, but they have no color at all.
Then, what is contained in the remaining "1"? It contains argon, carbon dioxide, neon, carbon monoxide, ozone, and a few others. If there had been even one colored substance in the air, the air would have been somewhat colored. Unfortunately, however, they are also colorless. This is why the air is invisible to our eyes.

The fact that gases are colorless means that the molecules of each gas do not reflect or diffuse light of a particular wavelength.