H absorbs very specific wavelengths, leaving almost all wavelengths undisturbed. So it is almost colorless. Also, it can take a long path through the gas before much is absorbed.

Those wavelengths are the same that are produced in a gas discharge lamp, which is not at all colorless. The reason is that the lamp produces lots of light at those wavelengths. The excess is very noticeable.

H absorbs very specific wavelengths, leaving almost all wavelengths undisturbed. Also the excited atoms then decay, producing the same wavelengths that were just absorbed.

Those wavelengths are the same that are produced in a gas discharge lamp, which is not at all colorless. The reason is that the lamp produces lots of light at those wavelengths. The excess is very noticeable.