Diarium version: 2.9.84
OS + version: 15.4.1
Device model: iPad Pro
The color of the tags can be chosen and confirmed with a „Save“ button. The colors are confirmed changed but nevertheless will this leave the colors of the tags in the timeline unaffected and unchanged.
It makes no difference if the colors are changed by choosing single the tag editor or below an entry of the timeline.
Edit: Restarting the application will solve this bug.