This little plugin lets you add your own stylesheet to the TXP Admin Interface so that you can customse it with your own styles. All you need to do is install + enable this plugin and create a new stylesheet via Textpattern named admin.
It also ID’s the
<body> of each section, eg
<body id="event_article"> so you can target styles to specific Admin sections.
Bare in mind that TXP prevents plugins from operating within the plugins area itself, so you can’t change the style of that section.