Circle Stitch
As you can see here, its spnnning on its axis. You need to know how to do the Square stitch to do this one.
Make 2 diagonal loops with one color
Put the opposite color over the first and under the second one DIAGONALLY
Put the second opposite color over the first loop and under the second one. DIAGONALLY
After you pull it tight, it sould look a lilttle like a circle.
And right after you pull that stitch, you should see it starting to change.