Here’s what I’ve been trained to think it means:

• 1 plugin needs attention
  (As in, “you’re not quite done installing a plugin, you need an API key or something.”)
  or
• 1 plugin just got installed. Or enabled. Or disabled.
  (And this notification will soon fade away.)

Sometimes it was red.

Sometimes it was grey.

Here’s what it actually meant:

An inactive plugin that came with my install, WP-Super-Cache,was eligible for an upgrade. This was installed via Dreamhost who may have packaged some dormant plugins. I have no idea at the moment whether non-Dreamhost installs will run into this.

I guess it’s a variation of the “needs attention” design pattern, but given that it was an inactive plugin, and the status of the available upgrade wasn’t particularly prominent or connected or linked-to from the Plugin (1), I know I’m not the only one who’s been stumped by this. I won’t name names, but a WP vet I asked didn’t know either.

GUESS WHO’S NOT CRAZY.

The more you know.