Update app.py

app.py

@@ -142,7 +142,7 @@ body {
     position: relative;
 }
 button, .button {
-    background-color: #4299e1;
+    background-color: #4a4a4a;
     color: white;
     border: none;
     padding: 0.5rem 1rem;
@@ -153,7 +153,7 @@ button, .button {
     line-height: 1.25rem;
 }
 button:hover, .button:hover {
-    background-color: #3182ce;
+    background-color: #2d2d2d;
 }
 .no-papers {
     text-align: center;