Artist Ko Yang designed this milk carton to change colors over time. That way, if it’s old, it should reveal its non-freshness without a sniff test. The box changes from all white to all cheese. Cheese, in this case, is a color represented by some kind of nasty looking orange splotches.
If it looks like cheese, you probably shouldn’t drink it. Ko Yang has a good idea here for consumers, although sellers might not be so quick to jump at this idea.