You can't rely on colors to indicate status because someone might be colorblind. That's an often overlooked problem. You have to make the light do something special, like blink, if you really need it to indicate something important.
About 5% of men have some kind of colourblindness. It is common enough I would argue it's good engineering and design to avoid using colour to indicate anything important, particularly when avoidable. Red-green rather than light-dark for intensity maps are particularly infamous. Any time I see one of those posted on a forum and it gets traction, some poor commenter complains at the colour choice because they can't see red-green distinctions. Saw such on HN just the other day.
