Update app.css

app.css

@@ -73,7 +73,7 @@ h1 {
 
 .box {
   border: 1px solid white;
-  background-color: #A2A2A2 !important;
+  background-color: #454545 !important;
   text-align: center;
   margin: 10px;
   padding: 5%;