There is a very good 'Sticky' marked Success Express which tells you all you need to know.
Basically, any foods 'free' on Extra Easy (which also means they're free on either Green or Red plans) are also free on Success Express.
You need 2/3 Superfree to 1/3 Free foods on your plate, you can have two lots of Healthy Extras, and snacks should be Superfree. You can still have up to 15 Syns a day but you count Syns at the highest value, so if you choose to have a Pasta n sauce type snack you would take the Syn value from the Red day.( Many Syns are, of course, the same on all plans - ketchup, jam etc.)
Do hunt out the sticky for full details and menu ideas.