[kronolith] Cannot change color/colour of other users calendars (Shared Calendars)

[Major Lazor]

> When clicking the edit-pencil next to a calendar of my own, the text
> field with the hex values of the rgb code is editable and there is an
> icon next to it with tooltip "Color Picker", so I can change the color
> of the calendar. The same for Remote Calendars.
>
> For Shared Calendars the text field is not editable and the "Color
> Picker"-Icon is missing. According to build+horde (at) de-korte (dot)
> org on the bug tracker (s)he can change the color of Shared Calendars
> https://bugs.horde.org/ticket/14978.
>
> search terms "calendar color" or "calendar colour" do not return
> relevant bug tickets
>
> Kronolith H5 (4.2.23) (Yes, I know, I already filed an update request)
> Groupware 5.2.22
>
> This is not an user-specific issue, I tested this with 2 regular users.
>
> Did anyone see this before?
>
> Thank you.