IE tabs colour

[The Stealthinator]

When the tabs in IE change colour, what does that mean?

 

[USAFRet]

http://windows.microsoft.com/en-us/internet-explorer/products/ie-9/features/enhanced-tabs

"With Internet Explorer 9, tabs that are related are color coded, making it easier to stay organized while browsing multiple webpages."
"When you open a new tab from another tab, the new one is placed next to the first tab and is color coded to match"