Make Active Admin's primary color change between dev/staging/production

active_admin.scss

// SASS variable overrides must be declared before loading up Active Admin's styles.
//
// To view the variables that Active Admin provides, take a look at
// `app/assets/stylesheets/active_admin/mixins/_variables.css.scss` in the
// Active Admin source.
//
// For example, to change the sidebar width:
// $sidebar-width: 242px;

$primary-color: dynamic_active_admin_color();

// Active Admin's got SASS!
@import "active_admin/mixins";
@import "active_admin/base";

// Overriding any non-variable SASS must be done after the fact.
// For example, to change the default status-tag color:
//
//   .status_tag { background: #6090DB; }

application.rb

if config.respond_to?(:sass)
  require "#{config.root}/lib/sass_ext.rb"
end

sass_ext.rb

module Sass::Script::Functions

  module ActiveAdminEnvColor

    def dynamic_active_admin_color
      color = case Rails.env
      when 'production'  then [0x5e, 0x64, 0x69] # grey (default AA)
      when 'staging'     then [0x45, 0x77, 0x4b] # green
      when 'development' then [0x84, 0x4c, 0x62] # red
      end
      Sass::Script::Color.new color
    end

  end

  include ActiveAdminEnvColor
end