Commentary:

As a character Magenta is already a resident of Grumbletown before the comic starts, so the others know her, but she exists slightly outside Red, Blue, and Green’s clique. She runs the town’s only store, which is grey right now because I had decided that since the people were so colorful the things they surround themselves with probably would be more drab. You can see this again at Magenta’s birthday party, where all of the balloons are grey, too.

Here Yellow has just told Magenta some scandalous gossip.