Name 3 gases which is visible for us?

There are several colored gases and of course the colors are visible, but colorless gases are not visible. There is a lot to learn about this question, so study some links: www.google.com/search?q=visible+gases

NOTE: The sky is blue because the molecules deflect red light, not because air is blue. If air were blue the sky would only be bright on the side where the sun is, and it would be dark on the other side.