Retain hero background color (#2074)

Author: dsuren1

geonode_mapstore_client/client/themes/geonode/less/_variables.less

@@ -12,3 +12,5 @@
 @ms-font-family-base: 'Montserrat', sans-serif;
 
 @ms-primary: #397AAB;
+@ms-jumbotron-bg: #0c3756;
+@ms-jumbotron-color: #ffffff;