EventBars/Details for supervisions are not differentiated enough from lessons

The following discussion from !301 (merged) should be addressed:

• @yuha started a discussion:

  FIXME: EventBars/Details for supervisions are not differentiated enough from lessons

changed milestone to /AlekSIS%"[NLnet #1 (closed)] Fix existing bugs with new timetable"

added part::frontend type::bug labels