Without much rambling, a solution for the problem presented in the title: http://code.google.com/p/qlcolorcode/

To change the color style (theme), use the following command:

defaults write org.n8gray.QLColorCode hlTheme [theme name]

Where [theme name] can be:

acid, bipolar, blacknblue, bright, contrast, darkblue, darkness, desert, easter, emacs, golden, greenlcd, ide-anjuta, ide-codewarrior, ide-devcpp, ide-eclipse, ide-kdev, ide-msvcpp, ide-xcode, kwrite, lucretia, matlab, moe, navy, nedit, neon, night, orion, pablo, peachpuff, print, rand01, seashell, slateGreen, the, typical, vampire, vim-dark, vim, whitengrey, zellner

More customization info here.

Have fun!