I haven't tried it yet but I know people whi have and they say it works!
At each meal time you can have either a 'red' meal or a 'green' meal. In between meals, you can only eat food that are free on BOTH days.
You still have the same number of healthy extras. If you are having a 'green' breakfast, you can choose healthy extras from the 'green' list and same if you were having a 'red' lunch, choose from the red list. As long as you still have the same number of HE's its ok.