Andon is a kind of visual management, which is used to address informaton deficit and provides an immediate and real-time understanding of what the situation is. In my current company, there are several colors for Andon
(1) When material needs to replenished
(2) When machine breaks down
(3) When a quality issue occurs
Different color indicates different scenarios. What is important is that when Andon is on, which means abnormal conditions, actions must be put in place to bring the abnormal suitation back to normal situation, othewise, you just creates more waste, which is useless.