Rated 4 out of 5 stars

Now I can see event by category color only (and do not see calendar color at all) :(

Can I see both colors in event (50/50): 1 - calendar, 2 - category?

This review is for a previous version of the add-on (4.0). 

Coloring event with category color

With the latest version of Calendar Tweaks, you have the option to color event backgrounds with the category color, instead of the normal calendar color.

This feature can be enabled/disabled as follows:

- Select Tools on the Thunderbird main menu, and then select Add-ons to show the Add-ons Manager
- Select the Extensions tab
- Click on the Options button in the Calendar Tweaks entry
- Enable or disable the "Apply category color to event backgrounds" option.