Stars are classified by their color, which is a direct indicator of their surface temperature. Here's a breakdown of the stellar classification system based on color:

Spectral Classes (Hottest to Coolest):

* O: Blue, extremely hot (30,000 K - 50,000 K)

* B: Blue-white, very hot (10,000 K - 30,000 K)

* A: White, hot (7,500 K - 10,000 K)

* F: Yellow-white, moderately hot (5,000 K - 7,500 K)

* G: Yellow, moderate temperature (3,500 K - 5,000 K) - Our Sun is a G-type star.

* K: Orange, cool (2,500 K - 3,500 K)

* M: Red, coolest (2,000 K - 2,500 K)

Important Notes:

* Color is relative: Stars can appear different colors depending on their distance and the amount of dust and gas between them and us.

* Other factors: Stars are also classified based on their luminosity, size, and composition.

* Subdivisions: Each spectral class is further divided into subclasses, such as B0, B1, B2, etc., with the numbers indicating finer temperature gradations.

Examples of Stars by Color:

* Blue: Rigel (B8Ia), Spica (B1V)

* Blue-white: Sirius (A1V), Vega (A0V)

* White: Procyon (F5IV-V)

* Yellow: Sun (G2V), Capella (G8III)

* Orange: Arcturus (K1.5III)

* Red: Betelgeuse (M2Iab), Proxima Centauri (M5.5Ve)

Remember, the color of a star is a powerful tool for understanding its characteristics and place in the universe.