This is so simple, but if you jump be6ween Live, Staging, Development btaches of your website, so when you post office post like "Kerran from Dev Team's turn to make he teas and coffess" on your national newspaper site... you know it's a joke on the development and note a real thing.
If in your theme is developed by yourself, or you're using a child schenme, you can also on the front-end do a big banner in red to day "OFFLINE SIE"
To get them to change colour, just go into the User's profile, and edit the "Admin colour Scheme".
