Why does Google Calendar use a RED ‘Loading…’ overlay

I've noticed that Google Calendar uses a red Loading... overlay in the top righthand corner on Ajax actions (e.g. opening a calendar item):

I know that Google, being Google, have redefined the usual emotive connection of RED (error/danger) for their primary buttons, e.g. SAVE (see What rules does Google use to make a button gray, blue, or red on their sites?), but is red a good color to indicate something as unobtrusive as 'Loading'?

Incidentally, it doesn't seem that they have a company-wide standard in this regard: Google Drive, for example, uses the color-flipping ball, and it's over the specific div, not top-right: