The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula situated south^[b] of Orion's Belt. It is one of the brightest nebulae, and is visible to the naked eye in the night sky. M42 is located at a distance of 1,344 ± 20 light years^[2][5] and is the closest region of massive star formation to Earth. The M42 nebula is estimated to be 24 light years across. Older texts frequently referred to the Orion Nebula as the Great Nebula in Orion or the Great Orion Nebula.
courtesy Oberlin College

The Pleiades nebula is a reflection nebula -- it glows with light scattered from nearby stars. In this case the stars are actually embedded within the nebula. The scattered light is blue for the same reason the sky is blue: blue light is scattered more than red light. The Japanese name for Pleiades is "Subaru" -- the car manufacturer took its name from this cluster of stars.

courtesy Oberlin College