When you create a graded activity, you can designate a passing score in the Grade options area.
You can take advantage of this feature in three ways:
Completion tracking—if you set completion tracking conditions for the item, you can require a passing score in order for it to be displayed as completed by the student.
Grade display—grades belong the passing score will be displayed in the instructor's gradebook in red, while those above will be displayed in green. (All grades are displayed in black in students gradebooks.)
Restrict access—release an activity or resource based on students having achieved a passing score on a prior graded activity.