First of all, Purple is the name of one of the menus under the "old" * plan, not the new Feel Full Plan; the new plans are numbered 1, 2, 3, etc.
I believe the confusion is that when the numbered plans were introduced, some people on purple went to Plan 2 and some to Plan 3. The decision as to which plan was chosen was dependent on weight, height, other factors.
On the monthly diary toward the top, it lists the number of the plan.
Hope this helps.
* I used "old" plan because I don't know what else to call in. Truth be told, many centers are still using the green. gold, purple, blue, red, etc plans.
Thinner is better...........