This is a class management tool.
I use it to reward the students who are in green zone at the end of class. Students in red and yellow zone when class is finished must pay a "fine" to be erased. My school uses a sticker system which is cashed out at the end of the year to buy things for the students, so our zones use stickers for rewards and fines. Use whatever you'd like (candy, treats, no assignments, extra breaktime, etc...)
Cut out the middle portion of the zone, laminate the rest, and add magnetic strips to the back portion. Then you can attach it to your chalkboard and write students' names in the cutout portion.