Simple Visual Poka Yoke at a Hotel

While staying at a hotel recently I noticed a simple visual poka yoke. Poka yoke is the Japanese term for mistake proofing. In this case a two cable phone jack is color coded and labeled to indicate the phone line and the modem line.

This picture is a little hard to see but the phone line is colored black and the modem line is colored red. Below you can see the red line or modem line connecting into a desktop port.

This visual prevents mistakes of plugging the phone or a computer into the wrong line. The simplicity of this poka yoke illustrates that solutions don't need to be costly or complicated.  I am impressed to see the hotel management embrace problem solving in a way that allows their employees to get involved.  Now any employee can reconnect the lines should they become disconnected. 

Many of us have lines at our home or office that we could use a technique like this to prevent plugging devices into the wrong lines.  What type of poka yoke solutions do you use in your work and living spaces?