--- a/devtools/client/themes/animationinspector.css
+++ b/devtools/client/themes/animationinspector.css
@@ -359,16 +359,20 @@ body {
   position: relative;
 }
 
 /* Display animations' background colors to alternate. */
 .animation-timeline .animation:nth-child(2n+1) {
   background-color: var(--even-animation-timeline-background-color);
 }
 
+.animation-timeline .animation.selected {
+  background-color: var(--theme-selection-background-semitransparent);
+}
+
 .animation-timeline .animation:last-child {
   margin-bottom: calc(var(--timeline-animation-height) / 2);
 }
 
 .animation-timeline .animation .target {
   width: var(--timeline-sidebar-width);
   height: 100%;
   overflow: hidden;