In this short film from PBS, scientists explain how we get those beautiful color photos from space -- despite much of the data coming back in black and white. In short: it involves a good deal of Photoshop manipulation, but is based on real data gathered from space telescopes. Take a look:
Sample quote from Zolt Levay on the process of false color imaging: "The colors are real. They may not be the exact colors that we see with our eyes, but the colors are true and real."
If you're into this kind of thing, you'll love the (totally safe for work!) "spaceporn" Subreddit. It's full of great space images, many suitable for computer desktop wallpaper.