You can edit your settings.xml of the skin that you are using (it's better to do a copy of the skin, and modify that settings.xml) and find something like this:
[code]
<General>
<Colors>
<balloonbackground>#daeafe</balloonbackground>
<balloonborder>#2e8afe</balloonborder>
<balloontext>#0000dd</balloontext>
<menubackground>#cce6ff</menubackground>
<menuforeground>#000000</menuforeground>
<menuactivebackground>#318eff</menuactivebackground>
<menuactiveforeground>#ffffff</menuactiveforeground>
</Colors>
[code]
If you know hex codes colors, you won't have any problem to change it. If you don't know, try with a graphic editor, or try this link to know some codes:
http://www.hypersolutions.org/pages/rgbhex.html
