The Department of Homeland Security’s Threat Advisory System (definitions here) is a great example of a bad metric.
No information is conveyed, the method of construction is opaque and the required action isn’t clear. For example, yellow includes “Continue to be alert for suspicious activity and report it to authorities.” and orange cites ”
Exercise caution when traveling.” Aren’t these things we should be doing anyway?
Despite these failings, at least the scale is vivid and simple. This doesn’t compensate for it’s other failings, but it’s one case that some information is worse than no information at all.