diff --git a/erpnext/www/book_appointment/index.css b/erpnext/www/book_appointment/index.css
index 2776108..3b1b97c 100644
--- a/erpnext/www/book_appointment/index.css
+++ b/erpnext/www/book_appointment/index.css
@@ -45,7 +45,7 @@
 
 .time-slot.selected {
     color: white;
-    background: #5e64ff;
+    background: var(--primary-color);
 }
 
 .time-slot.selected .text-muted {