While using iTerm2, I have noticed that sometimes the color of the title of a tab changes to pink with a loading indicator or changes to red. What do these things mean?
The iTerm color change of Tab labels indicates activity.
It can be turned of in: Preferences > Appearance > Color tab labels on activity
The help file explains this "Color tab labels on activity" appearance preference as follows:
If selected, tab labels become purple when a non-selected tab has new output, and red when a non-selected tab has output you haven't seen but that is not very recent.