Red dwarfs are by far the most common type of star in the Milky Way – at least in the neighborhood of the Sun. According to some estimates, they make up three–quarters of the stars in the Milky Way. Fifty of the sixty nearest stars to the Sun – including the nearest of them all, Proxima Centauri – are red dwarfs.
A red dwarf with more than about 25% of the Sun's mass will evolve into a red giant as it exhausts its supply of hydrogen, as does a yellow dwarf (like the Sun). Astronomers predict that a smaller red dwarf will become more luminous as it ages, turning into a blue dwarf; a blue dwarf will eventually evolve into a white dwarf once its hydrogen is completely exhausted.
There are no blue dwarfs actually in existence at the moment, as the Universe hasn't existed long enough for them to evolve!
© Haydn Thompson 2017