Since most of my students are in the first grade, I spend a lot of time with the general education first grade teachers, which has been a pleasure. Several of them refer to "moving clips" on their color charts, so I checked them out. The one I have used to illustrate this strategy is actually from a third grade classroom, whose teacher also shared the success she feels she has with this particular technique. I share this strategy in an article I just put up, A Color Classroom Behavior Chart Using Clothespins.
The idea has been spread by Rick Morris, a education speaker and consultant, who attributes it to his son's third grade teacher. He has a free brochure that describes this strategy on his site, New Management, in which he goes into more detail. Check mine out, and then visit his article if you have some questions.
Unlike a color card system, the clothespin system offers students opportunities to move back up by improving behavior and complying with teacher directions. It also starts everyone in the middle, on green, and gives the teacher an opportunity to recognize outstanding behavior and performance. In classrooms where we are asking students to collaborate in learning centers and on group projects, it's good to have a way to recognize leadership and self control. In classrooms that include children with disabilities, it offers opportunities to differentiate classroom management.