From Medarot S Wiki
There are two types of events currently:
- 激闘！ [Medabot Name] (Fierce Fight! [Medabot Name] which allows you to farm a featured Medabot to collect parts for it.
- Weekly Scheduled Robattles which are timed dungeons on a repeating schedule (see here for the weekly schedule).
They can be identified with their distinct option color, with Fierce Fights being Aqua and weekly dungeons being Dark Blue.