Here's why:

* Color and Temperature: The color of a star is directly related to its surface temperature.

* Blackbody Radiation: Stars emit light like blackbodies, meaning hotter objects emit more blue light, while cooler objects emit more red light.

* Spectral Class: Astronomers classify stars based on their spectral type, with O and B stars being the hottest (blue) and M and K stars being the coolest (red).

In summary:

* Blue Stars: Hottest, emit more blue light.

* Red Stars: Coolest, emit more red light.