The solid green light indicates that the market(s) is open and a price update can occur at any time.

The flashing green light means the market has opened but active trading hasn't yet begun. This is often the situation after New York has closed and the Sydney market is just waking up.

The red light goes on when the market(s) is closed. When it's displayed on the New York table the price shown is the day's market close. A red light on the Asia/Europe table simply reflects the last price quoted from what is usually the London Spot Market.

You will rarely see a yellow light since it indicates an irregularity somewhere. Reasons for displaying a yellow light in the Asia/Europe table could be that one of the major markets are on holiday. The New York table might display a yellow light if we feel the data may be less reliable than usual for whatever reason.

You will never see all the lights off since this would indicate that we are experiencing an electrical power failure. And then we wouldn't be able to upload the graphic, would we?