Think of food as a lifestyle choice rather than something to fiddle with for a few weeks, and you're more likely to make sustainable improvements, regardless of what your goal is -- healthy weight, fewer headaches, better digestion, more energy, etc. Sometimes you can find a standard diet that fits your needs well, and use that, but often you'll have to develop your own by learning which foods do what you want. Don't sabotage yourself by trying to jump into a really stringent diet all at once. Small changes are more likely to stick -- say, switching from white to brown rice (more fiber) or choosing vegetable side dishes over processed carbs (more nutrients, fewer calories).
Too much hype attracts people to fad diets. Look where those are on the list: mostly at the bottom. 0_o There are better options. The healthiest option is also among the easiest: the Mediterranean diet.
The red-yellow-green system just gives you general lists of things that are good to eat, okay, or indulgent. It's generally rigged for calories but you can make your own just by creating lists. Maybe you care more about how processed a food is than how rich it is. Green: unprocessed or home processed. Yellow: lightly processed. Red: ultra-processed. If you're a locavore you could make those distances instead. In any case, the more you can eat out of the green category, the better you meet your goals.