Usually you set color for tabs using the tab name and project name regular expressions in the Tab Coloring Rule dialog. If you want to color tabs by type (for example .cs or .xaml) you can use the document paths regex. But then there are form designer [Design] tabs that can’t be matched using the existing rules.
I’ve added the Tab extensions regex rule that complements the Tab name regex rule and lets you assign tab background depending on opened extensions in a tab group:
I’ve added the TabExtensions property to the Tab control that consists of the extensions list separated by ‘$’. For example, “Form2 .cs .cs [Design]” tab has “TabName=Form2” and “TabExtensions=.cs$.cs [Design]$”. Note, that a single tab like “Class1.cs” still has the name “Class1” and the extensions “.cs$”.
Download link: Tabs Studio v2.3.5.