ColorField (sometimes?) returns 8-digit alpha color hex code

...which causes problems when creating ExtraMarks, for example (since the backend wants "regular" 6-digit codes)

permcu: Also produces errors when creating or updating absence-reasons.

Relevant vuetify issue for hiding the transparancy-select: https://github.com/vuetifyjs/vuetify/issues/9590 Seems better with vuetify 3.0