Found a "fresh minted" article here that will help with the diet in the Body Friendly Zen Cookbook, but it needs a bit of clarification I think. Before you go rushing out and buying everything in sight based on colour... hehehe...
First, this article, as in so many others, barely mentions the words "fresh" nor "natural." Not as in "the kind my supermarket would have you believe but in fact we've stored this stuff for up to a year already and bombarded it with chemicals to keep it looking bright and fresh" but the kind of fresh you get from taking a vegetable that has ripened in the ground, been harvested no more than a few days ago, and brought all nice and cool and crisp to the market where you've taken it home and cooked it within a day sort of fresh and natural.
Because, if the fruit or vegetable has been treated to make it keep longer, it's now contaminated with chemicals that are NOT in the human species' diet plan. If it's been stored for any length of time, the active ingredients have lost their potency and you may as well eat coloured starch. And most importantly, if it's out of season, then for most fruits and vegetables we've lost the other great natural healing force, the Pulse. In the Body Friendly Zen Cookbook I mention the Pulse for a range of ingredients and how it's actually a large part of the effectiveness of the diet.
Also note that not all things that are brightly coloured are automatically good for one. The beautiful red colour of Amanitae mushrooms hides a potent toxin that kills flies on contact and can kill a human almost as easily.
Also, bear in mind that the things that give a food the colour and the tart taste are the ingredients we want? Of grapes, it's the skins and seeds (especially the seeds) which give the antioxidant effect, and that is why red wine (which is brewed with the skins and seeds in the vat) is effective while white wine (which is brewed from white grape juice only, no skins or seeds) is not. The old saw that the "goodness is in the skin" of a vegetable is for a large part the truth.
Can I put it any plainer? Old wives' tales had to originate from something. Our ancestors didn't all know how to read and write, but they knew how to pass on observations. The family down the road, that peeled the skins off their vegetables and ate mostly potatoes and very few others, their kids sickened every year. It's as valid an observation as any made by a scientist in their laboratory today, and the way we passed that knowledge on was by repeating it until it stuck and became an old wives' tale...
So if you have any old lore like that, it needs to be preserved. If you leave it in comments here, I will try and collect it inot a coherent and searchable web page every so often. Meanwhile, have a great day, and don't forget to eat your greens, and your reds, and your purples.