Andons are used in Lean
Production. The term refers
to the use of lights as visual signals.
Lights with three colors, red amber and
green are often used. Green is normal operations,
amber means routine action required, red
means abnormal action, immediate attentions.
For example an andon might be used to trigger
material replenishment. Green means no action,
amber means time to replenish and red means
stockout, immediate action required.