silverstripe-framework/admin/scss/_uitheme.scss

/**
 * This file defines CMS-specific customizations to the jQuery UI theme.
 * Every rule in this file should be wrapped in the '.cms' selector (to make it more specific),
 * and contain ONLY overwritten jQuery UI rules (with 'ui-' prefix).
 * 
 * This file should be fairly short, as we're using our own custom jQuery UI theme already.
 * TODO Add theme reference
 * 
 * Use _style.scss to add more generic style information,
 * and read the jQuery UI theming API: http://jqueryui.com/docs/Theming/API
 */

.cms {	
	.ui-tabs {
		padding: 0;
		
		.ui-widget-header {
			border: 0;
			background: none;
		}
	}
	
	.ui-widget-content,
	.ui-tabs .ui-tabs-panel {
		color: $color-text;
		font-size: 1em;
		border: 0;
		background: $color-widget-bg;
	}
	
	.ui-widget-header {
		background: $color-widget-bg;
		border: 0;
	}
	
	.ss-ui-button {
		padding: 5px;
		text-decoration: none;
	}
}