I don't agree that this is necessarily the case. I'm vegetarian and lost over 7 stone in 11 months doing mostly green ( I wasn't veggie at the time but ate very little meat preferring quorn). I actually lost more weight on the weeks where I ate no meat and only used meat sustitutes.
I love my carbs too and usually have them at two meals every day but I do still make sure I include a lot of superfree foods and not just a plateful of pasta. I also used a wide range of different free foods eg cous cous, quinoa, pulses, lentils, bulghar wheat and not just pasta and rice.
On those very rare days when I would try the red plan I was continually starving. If I had forced myself to do a lot of red days in the belief that it would make my losses bigger then I don't think I would have stuck with the plan and got to target. So you need to do what will help you follow the plan long-term and not just chase big weekly losses.