diff --git a/css/styles.css b/css/styles.css
index 0e638c9..56264d3 100644
--- a/css/styles.css
+++ b/css/styles.css
@@ -613,7 +613,7 @@ section { padding: 64px 0; }
 
 /* ---------- Diagram-style project thumb ---------- */
 .project-card .thumb-diagram {
-  background: #ffffff;
+  background: #13283c;
   display: flex;
   align-items: center;
   justify-content: center;