At this magnification the whole nebula has an a blue green hue that is in contrast to its actual red color. These great examples of open clusters with a surprise in M46. That is a planetary nebula that is not actually a member but a foreground object. This illustrates to me 2 different stages of evolution of stars. The open cluster is that of early Main Sequence.
Current theory holds that open clusters are transitory objects.
While all the stars in them are of about the same age and formed from the same nebula, they cannot maintain this association with the other stars. Gravitational effects from other stars the galaxy and such will cause the cluster to break up over a period of a few million years. Planetary Nebula are the end result of Stellar Evolution. In the final few thousand years of most stars they throw off their outer atmospheres. Many times it appears to us a small disk resembling in angular size the planets Neptune and Uranus thus the term planetary nebula.