Is it possible to assign certain parts? I'd like to assign time and colors not verbs etc.
I'd like to assign time and colors as beginner skills, but my students report that to do those things they need to complete the verb être, plurals, and other things they are not ready for before then.
No, you cannot create your own course, you need to follow the one Duo created. The verbs introduced early are pretty essential to create/understand very simple sentences such as I am, you are, i want, I speak etc which are useful in forming sentences about other vocabulary including colours etc.
If you want to teach simple vocab for colours and time etc. You need to look for a suitable Flashcard app such as Tinycards, Memrise and Anki etc.