Much improved over the simple v1.0!
The emphasis is still on coloring the active tab for easy recognition, and avoiding closing the wrong one.
But since changing the tab color is an "all or nothing" action, requiring creating a new theme, we've added a color chooser for the user Interface (UI). This basically lets you create a simple theme on the fly.
There is a drop-down menu that saves your last five UI color selections, and allows previewing them by holding the mouse pointer over any entry in History. Clicking that entry will re-apply that color. If you do not want to apply any of the saved colors, click away from the drop-down.
Also new, are check boxes to keep default UI color, and there is now a night mode that applies a soft black theme for working at night or in low light with out the eye strain of a light theme.