Since I originally compiled this list the number of relevant images has grown tremendously. I cannot hope to keep up with them all. If you don't find what you want here, try the references below.
Note: most of the pictures here are not true color. Most of them were created by combining several black and white images taken thru various color filters. Though the colors may look "right" chances are they aren't exactly what your eye would see.
... Appendices
... Hypotheticals
... Pictures
... Credits
... 