diff --git a/src/wp-admin/css/colors-fresh.css b/src/wp-admin/css/colors-fresh.css
index 1bc205e4c1..197a3fbf7a 100644
--- a/src/wp-admin/css/colors-fresh.css
+++ b/src/wp-admin/css/colors-fresh.css
@@ -1312,6 +1312,20 @@ table.widefat .spam a:hover {
 	color: #fff;
 }
 
+/* Collapse button in theme preview */
+
+.wp-full-overlay a.collapse-sidebar {
+	color: #777;
+}
+
+.wp-full-overlay a.collapse-sidebar:hover {
+	color: #0074a2;
+}
+
+.wp-full-overlay .collapse-sidebar-arrow:before {
+	background: #eee;
+}
+
 /* Diff */
 
 table.diff .diff-deletedline del {
diff --git a/src/wp-admin/css/customize-controls.css b/src/wp-admin/css/customize-controls.css
index 601bc13f1d..3ebb07239a 100644
--- a/src/wp-admin/css/customize-controls.css
+++ b/src/wp-admin/css/customize-controls.css
@@ -222,18 +222,6 @@ body {
 	border-radius: 0 !important;
 }
 
-.collapse-sidebar .collapse-sidebar-label {
-	color: #ccc;
-}
-
-.collapse-sidebar .collapse-sidebar-arrow:before {
-	color: #aaa;
-}
-
-.collapse-sidebar:hover .collapse-sidebar-label,
-.collapse-sidebar:hover .collapse-sidebar-arrow:before {
-	color: #0074a2;
-}
 
 .collapse-sidebar:active,
 .collapse-sidebar:active .collapse-sidebar-label,
diff --git a/src/wp-admin/css/wp-admin.css b/src/wp-admin/css/wp-admin.css
index 15b1cf0965..e603fdbb98 100644
--- a/src/wp-admin/css/wp-admin.css
+++ b/src/wp-admin/css/wp-admin.css
@@ -7561,6 +7561,7 @@ body.full-overlay-active {
 }
 
 .wp-full-overlay .collapse-sidebar-arrow:before {
+	border-radius: 50%;
 	float: left;
 	content: "\f148";
 	font: normal 20px/1 'dashicons';
diff --git a/src/wp-admin/includes/class-wp-theme-install-list-table.php b/src/wp-admin/includes/class-wp-theme-install-list-table.php
index a4fc5ba83d..8934684c21 100644
--- a/src/wp-admin/includes/class-wp-theme-install-list-table.php
+++ b/src/wp-admin/includes/class-wp-theme-install-list-table.php
@@ -262,7 +262,7 @@ class WP_Theme_Install_List_Table extends WP_Themes_List_Table {
 					<div class="install-theme-info"></div>
 				</div>
 				<div class="wp-full-overlay-footer">
-					<a href="#" class="collapse-sidebar button-secondary" title="<?php esc_attr_e('Collapse Sidebar'); ?>">
+					<a href="#" class="collapse-sidebar" title="<?php esc_attr_e('Collapse Sidebar'); ?>">
 						<span class="collapse-sidebar-label"><?php _e('Collapse'); ?></span>
 						<span class="collapse-sidebar-arrow"></span>
 					</a>