Hi @Adam-Involute! Very good question. I checked this from my side and I can see the color of the task in your calendar view is actually correlated to the first project/tag you added to your task. Let’s say, if you added the project color first, the task will show the color of the first project you linked to this task.
You can check more information in this post: Tasks showing tag colour instead of project colour in team calendar
I hope this helps, let me know if you have any questions.