Fix placeholder text color for file inputs/uploads.

web/app/static/css/nopaque.css

@@ -19,6 +19,12 @@ main {
   font-weight: bold;
 }
 
+/* Change placholdertext color of file uplaod fields */
+::placeholder { /* Chrome, Firefox, Opera, Safari 10.1+ */
+  color: #9e9e9e;
+  opacity: 1; /* Firefox */
+}
+
 /* preloader circle in the size of a button icon */
 .button-icon-spinner {
   bottom: -5px !important;