Tags
Events in markwhen can be tagged with the # syntax:
mw
2020: Mostly uneventful year #covid
Here, the event has the tag #covid. In views that support different colors, this event will have a distinct color from other, untagged events.
Colors
You can specify a tag's color in the header:
mw
---
#covid: blue
---
2020: Mostly uneventful year #covid
Multiple tags
Events, groups, and sections all support multiple tags, but their behavior with given properties becomes undefined -- or at least less defined.
Basically, do not expect smart merging of tags' properties:
mw
#school: red
#work: yellow
2021: Was working while in school #school #work
Events tagged with both #school and #work will not be colored orange because #school is red and #work is yellow. It will be one or the other. Similarly with timezones -- an event can't simultaneously have two different timezones. You should be specific with your tags.