1. Temperature:

* Blue stars: Extremely hot with surface temperatures ranging from 10,000 to 50,000 Kelvin (K).

* Red stars: Much cooler with surface temperatures ranging from 2,500 to 3,500 K.

2. Size:

* Blue stars: Usually much larger than red stars. They are considered "giants" or "supergiants."

* Red stars: Can be much smaller than the sun, or even "red dwarfs" which are the smallest and coolest stars.

3. Mass:

* Blue stars: Much more massive than red stars. They can be up to 100 times more massive than our Sun.

* Red stars: Much less massive than blue stars, often only a fraction of the Sun's mass.

4. Luminosity:

* Blue stars: Incredibly bright and luminous, often shining thousands or even millions of times brighter than our Sun.

* Red stars: Relatively faint and dim, with a luminosity far lower than our Sun.

5. Lifetime:

* Blue stars: Short-lived due to their high mass and energy output. They burn through their fuel quickly and may only exist for a few million years.

* Red stars: Long-lived due to their low mass and slower energy consumption. They can burn for billions or even trillions of years.

6. Composition:

* Blue stars: Mostly composed of hydrogen and helium, but may contain heavier elements.

* Red stars: Similar composition to blue stars, but may have slightly lower proportions of heavier elements.

7. Spectral Classification:

* Blue stars: Belong to spectral classes O and B.

* Red stars: Belong to spectral classes M, K, and some G.

8. Evolution:

* Blue stars: Eventually explode as supernovae, leaving behind neutron stars or black holes.

* Red stars: May evolve into red giants and then white dwarfs, or in the case of massive red stars, explode as supernovae.

In summary:

Blue stars are incredibly hot, massive, and luminous, while red stars are relatively cool, small, and faint. Their differences stem from their distinct masses and corresponding energy output and lifespans.