Ozh has put up a tutorial on how everyone can change the colour schemes of the WordPress 2.5 administration panel. It seems to be relatively simple, if you understand how to make a plugin.
WordPress 2.5 introduces a neat option: per user Admin Color Scheme. This means that each user can select a stylesheet they like best for the whole admin area. Now onto the fun stuff: adding a per-user selectable custom stylesheet for your blog.
The new function behind this feature is wp_admin_css_color(),
I have to admit, I wish a build-a-colour-scheme tool was built right into WordPress 2.5. Here is hoping that someone comes up with a good plugin solution for it, but until then, this is a great tutorial on how to change the colours to your own preferences.