Offering the various colors and the options to modify is a move in the right direction, but as is -- these colors will be disorienting.
LATE: Changing from Pink to Green is not only going to confuse users used to the pink, but Green is also misguiding as it's a positive or affirming color elsewhere in a Canvas and related technologies. RECOMMEND: Keep Pink.
MISSING: I trust assignments will only appear missing if they're past a due date. Otherwise, I'm not sure how this works. Color wise, pink is confusing b/c is used to mean late. RECOMMEND: A darker pink given it's the next stage after Late, which should remain pink.
RESUBMITTED: Perhaps blue would work for this...As is, it's too close to Missing.
DROPPED: Keep the light gray that is in the current grade book.
EXCUSED: Keep the EX and light gray. Adding additional colors is a serious overload here.