Calendar block colour/thumbnail customisation

I'm trying to create a calendar view that is colour coded to differentiate between types of event, like in this screenshot.

I know CSS will allow me to make all event days the same colour, but I need multiple colours. I've tried cheating by giving the events a header image that's just the colour I'd like them to appear on the calendar, and this sort of works, but I'd ideally like to be able to use a slimline calendar below 600px and I can't figure out how to force the thumbnail to appear on that calendar.

Does anyone know either how I can use CSS (and presumably Javascript) to customise date colour on the calendar by event tags, or how I can force an event thumbnail to appear on a slimline calendar?

Thanks.

Our site is here https://www.butserancientfarm.co.uk/whats-on

1 hour ago, ButserFarm said:

I'd like them to appear on the calendar

Can you direct me to the Calendar Block view? I could only see the Events page.

1 minute ago, paul2009 said:

Can you direct me to the Calendar Block view? I could only see the Events page.

I've been testing the calendar block here: https://www.butserancientfarm.co.uk/new-page-4

I checked but Squarespace's Calendar Block is now very old (it hasn't received any love recently) so doesn't have CSS selectors for tags or categories. This means it isn't possible to do this with CSS.

It may be possible to achieve it with JavaScript but nothing was immediately obvious as you'll be fighting with Squarespace's own JavaScript, used to create the calendar block. 

Others may have ideas.