Folder tab turning red

What does it mean when a folder tab turns red? Earlier today I noticed two of my tabs turned red while in dual display mode. The two tabs were pointing to two different folders on two different hard drives. Not sure what I clicked or did to make them turn red, but after closing one of them the other one turned back to its normal color like all the rest of my tabs. So it appears the two tabs that turned red were somehow linked. I've never seen this happen before. If someone could clarify what actually happened, I would appreciate it.

The two tabs were linked to each other.

Right click either tab and use the Link option in the menu to unlink them.

I think holding alt and clicking a tab will link it, which could be how you triggered it by accident if notnusing the menu.

More on linking here: ... s/Tabs.htm