Any links to how to do this? My google-fu seems to be failing me. I'm assuming you somehow set things up so it automatically detects the page / content (based on the environment name or instance tags??) and changes the background?
<body style="foo bar baz env-#{Rails.environment}">
Then use CSS like you would normally on body.env-production, body.env-development, etc. <body class="foo bar baz env-#{Rails.environment}">Could make a nice Chrome extension...