Your 2.5 admin interface was officially pimped.
WordPress 2.5 introduces two new color schemes to your admin area: Classic and Fresh - If you dislike both, try JP Admin Stylish Blue. This plugin adds the additional color scheme "Stylish Blue" to your admin area. The custom style bases on the classic WordPress color scheme and was pimped up a little bit for more style, clearness and readability.
For more information, questions or feedback go to http://johannes.jarolim.com/jp-admin-stylishblue.