I know I'm not alone with the frustration that comes with living with a family who don't appear to be capable of checking whether a dishwasher is clean or dirty before taking items out or placing more items in. Arrgh!
This signage should help. You're welcome.
Made from a combination of high quality bamboo and white acrylic, with magnetic strips on the back.
Measures 15cm diameter - large enough to be noticed ;)