On the new calendar, their name always comes first.

Whenever I open the schedule for the new month, I see my colleague’s name first. Mine doesn’t show up until much later.

Scenes

On the new calendar, their name always comes first. — My colleague’s name goes first on the new monthly schedule, and mine is always farther down. Again, I turn the page without asking why.
The person who decides is off the calendar — Last month, the team lead assigned the work to that colleague first, too. They didn’t explain why to me, and the new monthly schedule doesn’t list any criteria.
Look at the pattern and the reason separately — When I look at workplace conflict, I separate the repeated assignments, the reason the team lead gave, and whether that reason was the actual criterion. That way, I can check whether favoritism is really at play.
Pick one line from the calendar — Tonight, pick one line showing a repeated assignment and write down the work listed and the reason the team lead gave. If you weren’t given a reason, write that down too.
A short question is enough — Once you’ve looked over your notes, you could ask: “I’d like to understand what criteria were used to assign this work.” It starts by asking about the assignment criteria.
Look again after hearing the reason — Lining up the criteria the team lead gave with the actual assignments can make it clearer where the thought of favoritism came from. For today, checking one line on the calendar is enough.