... As an experiment, I made some three-color images of Messier 42, more commonly known as the Great Nebula of Orion. ... green enhanced . ... halfsize or fullsize . ... Each image is a ``true color'' composite of three monochromatic images, in which the red, green, and blue intensities each correspond to the intensity of one of the original images. ... The HST image is assembled from different filters than mine: red is Nitrogen [II] at 6583 , green is H-alpha at 6563 , and blue is O [III] at 5007 . ...