@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

.tabbrowser-tab[selected="true"] > hbox,
.tabbrowser-tab[selected="true"] > .tab-close-button {
  background-color: #00f !important;
  color: #fff !important;
}

.tabbrowser-tab[selected="true"]:hover > hbox,
.tabbrowser-tab[selected="true"]:hover > .tab-close-button {
  background-color: #66f !important;
  color: #fff !important;
}

/* the rules below are optional, you can remove them */

.tabs-bottom {
  background-color: #00f !important;
  height: 6px !important;
}

.tabs-bottom-spacer {
  height: 2px !important;
}