Blue dwarf (red-dwarf stage)

Because red dwarfs fuse their hydrogen slowly and are fully convective (allowing their entire hydrogen supply to be fused, instead of merely that in the core), they are predicted to have lifespans of trillions of years; the Universe is currently not old enough for any blue dwarfs to have formed yet.

This is because the surface layers of red dwarfs do not become significantly more opaque with increasing temperature, so higher-energy photons from the interior of the star can escape, rather than being absorbed and re-radiated at lower temperatures as occurs in larger stars.

[1][2][3] Of the masses simulated, the bluest of the blue dwarf stars at the end of the simulation had begun as a 0.14 M☉ red dwarf, and ended with surface temperature approximately 8,600 K (8,330 °C; 15,020 °F), making it a type A blue-white star.

[1] Once the former "blue"-dwarf stars have become degenerate, non-stellar white dwarfs, they cool, losing the remnant heat left over from their final hydrogen-fusing stage.

The cooling process also requires enormous periods of time – much longer than the age of the universe at present – similar to the immense time previously required for them to change from their original red dwarf stage to their final blue dwarf stage.