Very simply
Red Days. Unlimited Meat, and Superfree foods (Veg, fruit, eggs) NO Pasta, rice, potatoes, parsnips, peas, sweetcorn, beans. 2 HEB & 2 HEA. Can use your HEBS for measured amounts of potato (with skins) or pasta (WM only)
Green Days; Unlimited Pasta, rice, potatoes, parsnips, peas, sweetcorn, beans. and Superfree foods (Veg, fruit, eggs). NO meat or fish. 2 HEB & 2 HEA. Can use your HEBS for measured amounts of lean meat or fish. Get an extended range of HEA's as well.
5-15 syns on either plan a day.
You can however, easily take a extra easy lunch which can be eaten on the go if necessary. Pasta Salad, Cous Cous Salad, Leftovers, soup.You can buy a thermos food flask for £20 on amazon, heat up leftovers or soup in the morning in the microwave and take to work. The food flask even has a proper spoon in the lid so you don't have to worry about how you will eat it, and it keeps food hot for about 7 hours.