Hello,

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information.
Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

Thank you.

I'm not sure what you mean by "the tabs that are not open." Are those the background tabs on the tab bar? Or is the actual content missing?

When you resume your previous session, by default Firefox waits to reload the inactive tabs. If you want them all loaded immediately, there is a setting for that in the Tab Options: Tab preferences and settings.

If colors have changed on you, it's possible that your theme changed. You can check your installed themes (and which one is active) on the Add-ons page:

orange Firefox button (or Tools menu) > Add-ons > in the left column click Appearance

If it is the color of the tabs then this might have been a setting in Tab Mix Plus to distinguish specific (unread) tabs.