Here's why:

* Temperature: Cool stars have lower surface temperatures than hotter stars.

* Color and Temperature: The color of a star is directly related to its temperature. Cooler stars emit more red light, while hotter stars emit more blue light.

* Examples: Red dwarfs, the most common type of star in the Milky Way, are small and cool. Our own Sun, a yellow dwarf, is considered a medium-sized and medium-temperature star.