Color of Number in Ad Tabs

In the tabs for the ads that I’m using, some are red and some are blue. Is there any significance to the color? I ask because Ad Inserter is causing the sidebar of my site to get pushed to the bottom of the page intermittingly. I think it might be related to the Adsense ads, both of which have the tabbed numbers in red. The others are all in blue and not creating any issues. Curious if the color in some way indicates an error.