Its possible. I have done this in my calendar with the same calendar app you are using. You can see I have changed one of the events to a pink:
I created a field in my database called “colour” and as a text field, under the datatype “schedule” when I use that calendar I just do a search for the datatype schedules.
Then, I watch the below tutorial that shows you how to make a colour swatch and save it to your database (in my case Schedule datatype).
Then, when you choose the event colour, and choose the source as your data type *in my case Schedules) datatype, you simply choose the event colour to be the field name “eg Event Colour” text value.
Instead of making a change to the ‘current user’ like in the tutorial I would either: add the swatch choosing part on to the schedule creation part (the datatype that is connected to your calendar).
Or what I did is created a datatype called Clients, where I created a data field called Colour (text). Then when I create a new schedule, I save the Colour as “search for clients”: first item “colour”
Heres the tutorial I used
How to change color dynamically from front end in Bubble.io #bubble #nocode #tutorial - YouTube
Also, you might find helpful this video, by Echo Lake Technologies, it shows you how to add extra values to your calendar: Calendar video #2: Add Calendar Plugin to Your Bubble.io No Code Web App - YouTube