View source for MediaWiki:Monobook.css

/* Background colors for content actions */
/* NS Project + Project_talk (light sky blue) */
.ns-4 #p-cactions li,
.ns-4 #p-cactions li a,
.ns-5 #p-cactions li,
.ns-5 #p-cactions li a {
	background: #f8fcff;
}

/* light grey */
/* NS Special */
.ns--2 #p-cactions li,
.ns--2 #p-cactions li a,
/* NS MediaWiki + MediaWiki_talk */
.ns-8 #p-cactions li,
.ns-8 #p-cactions li a,
.ns-9 #p-cactions li,
.ns-9 #p-cactions li a {
	background: #f4f4f4;
}

/* NS Manual + Manual_talk (light bluish violet) */
.ns-100 #p-cactions li,
.ns-100 #p-cactions li a,
.ns-101 #p-cactions li,
.ns-101 #p-cactions li a {
	background: #f3f3ff;
}