Hi there! So if you say that your workout is complete with a checkmark, but your day in the calendar is still showing as red --> that simply means that you have other tasks to complete that day.
Typically, it means that your coach assigned you a message you haven't opened, a survey you haven't completed, or a fitness test for you to complete.
Once you complete the additional tests, besides your workout --> your day will be completed and will no longer be the color red.