Red: a new proposition is added, in the form of a breaking test. When the proposition is made true by changing code, the next state is Green.
Green: the code passes tests of behavior. Working with a pair, examine the code and see if its current shape invites refactoring to improve how the code expresses its intention, or how it can recover or preserve properties useful to the team such as being readable or robust to changes in other parts of the code.
Refactor: Transform the code in small steps, keeping the behavior tests passing (Green), until the shape of the code expresses its intent and behavior clearly, and preserves useful properties.