Highlight exams in unit view

As I am teaching several classes it would be really helpful if I could highlight the lessons in which I want the students to write an exam, test, quiz or other kind of assessment. This would help to plan the exam dates in the unit view. One possibility to achieve that would be the option to assign a color to a certain lesson, (instead of only to the unit). So instead of always showing up as blue circles in the unit view, they could have different colors.