Rated 5 out of 5 stars

Firefox user 2d9a2a:
The add-on's author (DW-dev) is aware of the random problem. Not sure whether the problem is with the add-on or with TB. The previous version of this add-on worked perfectly on TB60 and before.

It delivers the correct category color option about 50% of the time, which is just one of the add-on's option features. Otherwise, the add-on works as designed.

I'm sure this little bug will be fixed in due time and the add-on will be automatically updated.

This review is for a previous version of the add-on (8.0).  This user has other reviews of this add-on.

This problem is fixed in Calendar Tweaks 8.1 which has been submitted to the Thunderbird team for review and release. This will probably take a few days.