diff --git a/doc/_static/custom.css b/doc/_static/custom.css
index 5fe1d2ba57..542a8a03f2 100644
--- a/doc/_static/custom.css
+++ b/doc/_static/custom.css
@@ -7,6 +7,15 @@ blockquote {
     background: #ecf0f1;
 }
 
+/* Sidebar header (and topbar for mobile) */
+.wy-side-nav-search, .wy-nav-top {
+    background: #00ff00;
+  }
+  /* Sidebar */
+  .wy-nav-side {
+    background: #ff0000;
+  }
+
 img {
     margin-bottom: 1em;
 }