What are those colored dots that run vertically on the side of a yogurt cup for?

Answer 1

those are a part of the package printing process, they indicate the colors used in the printing of the labels. they have no bearing on the yogurt contents. you will find those dots on most packages, usually in a hidden location, under box top flaps etc

Answer 2

that is called the color bar. It is used in the manufacturing of the plastic container to help maintain the proper color. a machine periodically reads the color and adjusts the press as necessary