Here's a breakdown:

* Spectral lines: When light from a star passes through a prism or diffraction grating, it splits into its component wavelengths, creating a spectrum. This spectrum shows dark lines, called absorption lines, at specific wavelengths. These lines are caused by elements in the star's atmosphere absorbing light at those wavelengths.

* Composition: The pattern of absorption lines in a star's spectrum reveals the chemical elements present in its atmosphere, and their relative abundances.

* Color: The overall color of a star is also related to its temperature. Hotter stars emit more blue light, while cooler stars emit more red light.

Therefore, by analyzing the spectral lines and color of a star, astronomers can determine its composition, temperature, and other properties.

Key takeaway: The unique combination of spectral lines and color provides a fingerprint for each star, allowing astronomers to classify them based on their composition and physical characteristics.