Gases are frequently described as "colorless, odorless, and tasteless." I am wondering if this is redundant, since I can't think of many gases that have a detectable color to begin with, much less ones that *have a color but no odor*. Are there any gases that are *colorful* and odorless at standard temperature and pressure? In particular, gases that impart enough of a color to white light that one could look into a room filled with the gas and detect its presence visually? (In the limit I suppose one could argue that a standard atmosphere is "colorful" since over many miles one can see blue scattering, but the question here is whether it is ever useful or helpful to describe a gas as "colorless.")