How can atomic emission spectra be useful?

The emission spectra of different are unique, so the spectra given off by hydrogen will be different than that of helium. The different colors of light produced by emission spectra of different elements allows them to be identified. One use of this technique is to identify the elements present in distant stars.

So elements can be identified by the colors their atoms produce when energy (by heating or electric current) is used to reveal their emission fingerprints. Analyzing the colors of light given off by stars reveals which elements are present in those stars.

Here is a look at emission (colors of light) produced by four different elements. Video from: Noel Pauller

Use of a tool such as a spectroscope would allow someone to determine the different wavelengths each of these elements is giving off. The color you observe in the video is the sum total of all of the visible emissions from each element.

Hope this helps!