Add a css updatable navbar color

app/assets/stylesheets/application.css.scss

@@ -35,6 +35,7 @@ $primary: $blue;
 
 $text: $grey-dark;
 $body-background-color: #FAFCFE;
+$light: #fff;
 
 @import 'bulma/bulma';
 

app/views/layouts/application.html.erb

@@ -16,7 +16,7 @@
   <div id="wrapper" class="has-text-centered-mobile">
 
     <!-- Hero -->
-    <section class="hero is-medium is-white">
+    <section class="hero is-medium is-light">
       <div class="hero-head">
         <div class="container">
           <nav class="navbar" role="navigation" aria-label="main navigation">