@Anonymous
So I created a dummy task, assigned to a couple of dummy colleagues. THis is my Flow design:

THis is the result of executing it:

Now, I assume you need to send a single email per task, no matter one or more colleagues were assigned to the task. If so, just need to add this step

I would probably add a 'Condition' action block in between, just to make sure there are at least one assigned to user.
If you are unfamiliar with WDL expressions, please follow these steps to add them:
https://youtu.be/LPZ-WZoWwp4
Please let us know your progress, if you find any issue implementing this approach do not hesitate to share a screenshot from your flow design and the problem encountered
Hope this helps