thanks Nate i didnt realize it was so big
j.p.s it looks to me like they are using the size of the red particle and possibly its native charge to help cycle the colors. they arent bigger in that GIF(hard g
) by accident and notice how they are never on the very bottom. when they first switch the change in polarity of the bottom may actually propel the black so that it sort of races and passes the red on the way to the top