find me a solution for this
Quick and dirty solution: Open the site in SharePoint designer, select the used master page and edit that, or edit the css linked to the masterpage.
(Works for one site only)
More robust solution: create a new theme and apply that to your site, the theme can be reused accros multiple sites.
If you don't know the css name of the element use the Developer Tools in IE 8 (press
F12) and select the element you want to style to find out the styles applied to that (and its name)