add color param to events

[rsgalloway]

currently events are just a list of lists of dates:

[
  ["3/14/2022", "3/15/2022", "3/16/2022"],
  ["3/28/2022", "3/29/2022", "3/30/2022"]
]

to support this feature we may need to change this to a list of dicts:

[
  {
    "dates": ["3/14/2022", "3/15/2022", "3/16/2022"],
    "color": "#ee2233"
  },
  {
    "dates": ["3/28/2022", "3/29/2022", "3/30/2022"],
    "color": "#11ee33"
  }
]