I have multiple calendars synced from Google. Two of them, Aki Tasks and Personal are the same colour. On my desktop they are the same colour, but on mobile they aren't. I think one of the colour dots is programmed incorrectly on mobile.

The first screenshot is on desktop, and shows what it should look like, with the all day event and the morning routine the same colour. The second screenshot shows what it looks like on mobile, with the all day event and morning routine showing up different colours. The third screenshot shows the calendar list on mobile, confirming that the two calendars are set to the same colour.