Fix a few remaining references to the old Theme names/IDs

app/views/layouts/devise.html.haml

 !!! 5
 %html{ lang: "en"}
   = render "layouts/head"
-  %body.ui_mars.login-page.application
+  %body.ui_charcoal.login-page.application
     = render "layouts/header/empty"
     = render "layouts/broadcast"
     .container.navless-container

config/gitlab.yml.example

@@ -62,12 +62,13 @@ production: &base
 
     # default_can_create_group: false  # default: true
     # username_changing_enabled: false # default: true - User can change her username/namespace
-    ## Default theme
-    ##   BASIC  = 1
-    ##   MARS   = 2
-    ##   MODERN = 3
-    ##   GRAY   = 4
-    ##   COLOR  = 5
+    ## Default theme ID
+    ##   1 - Graphite
+    ##   2 - Charcoal
+    ##   3 - Green
+    ##   4 - Gray
+    ##   5 - Violet
+    ##   6 - Blue
     # default_theme: 2 # default: 2
 
     ## Automatic issue closing

db/fixtures/production/001_admin.rb

@@ -12,7 +12,7 @@ admin = User.create(
   username: 'root',
   password: password,
   password_expires_at: expire_time,
-  theme_id: Gitlab::Theme::MARS
+  theme_id: Gitlab::Themes::APPLICATION_DEFAULT
 
 )