The colours seen in many Hubble Space Telescope photos are not necessarily an actual representation of the hues of the image subject, rather colour ranges are added later to separate, or emphasize, different aspects of say a star cluster or nebula.
Taking color pictures with the Hubble Space Telescope is much more complex than taking color pictures with a traditional camera. For one thing, Hubble doesn’t use color film – in fact, it doesn’t use film at all. Rather, its cameras record light from the universe with special electronic detectors. These detectors produce images of the cosmos not in color, but in shades of black and white.