Changing colors mid-round can be a way to add interest or color to a hat or applique that is being worked in the round.
I use this technique in the Bailey Bear applique pattern for the eyes and nose.
By working the color changes mid-round in the applique, I am able to integrate these features into the pattern. This means that they do not need to be embroidered on later.
This video shows how to make color changes mid round.