Hi Eran,
I have updated the plugin and have same problem with colors now:
1. In the WordPress Dashboard / Calendar / Categories, all of my categories are there and they all have the appropriate colours displayed.
2. Go the main Events calendar and all of the categories listed at the top are uncoloured.
3. Look down at events being displayed in the calendar and they are all highlighted in dark blue.
4. Look at the sidebar widget display and the events listed show no colour.
I did updated the categories as you suggested but it doesn’t help. You can see my calendar here: https://chinesegongfu.ru/calendar/
