Views and how to get calendar taxonomy legend
To see an option in the term field as above (e.g. field_event_type) make sure you add the Taxonomy field to your view and select Create a label in the Configure Field options. The label you create will then appear in the term field. If you do this with multiple term fields that are added to the view you can use the drop down to select.

Not sure at this stage regarding the Legend option however.