Visual indication of which pane is active for Atom

styles.less

/* this is the settings I use for the Solarized Light theme, change
 * the colors and loose the import if you're using another theme */

@import "variables";

.pane .editor-colors {
  background-color: @base2;
}
.pane.active .editor-colors {
  background-color: @base3;
}