These are not related. The color of a nebula is determined by the particular emission lines that are excited and O-B stars are very effective exciters of interstellar gas so red, green and yellow colors would be common in such 'emission nebulae'. I know of no true reflection nebulae that have these colors. Reflection nebulae I believe are usually blue due to dust grains which scatter the blue light most effectively as in the case of the Trifid Nebula companion for example. The nebula NGC 1999 in Orion is a beautiful example of a reflection nebula. Here's what the Hubble Space Telescope investigators had to say about the image at the top of this page:
NGC 1999 is an example of a reflection nebula. Like fog around a street lamp, a reflection nebula shines only because the light from an embedded source illuminates its dust; the nebula does not emit any visible light of its own. NGC 1999 lies close to the famous Orion Nebula, about 1,500 light-years from Earth, in a region of our Milky Way galaxy where new stars are being formed actively.
The nebula is famous in astronomical history because the first Herbig-Haro object was discovered immediately adjacent to it (it lies just outside the new Hubble image). Herbig-Haro objects are now known to be jets of gas ejected from very young stars.
Copyright 1997 Dr. Sten Odenwald
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