03/14/2011 02:32 pm ET Updated May 25, 2011

The 3 Colors You Should Be Eating More Of

By Brierley Wright, M.S., R.D., EatingWell Nutrition Editor

Remember ROYGBIV? I do. The mnemonic is how I learned the seven colors of a rainbow -- red, orange, yellow, green, blue, indigo and violet. Nowadays I use the acronym to represent the colors of food I should be eating.

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Because nature highlights the beneficial nutrients in fruits and vegetables by giving them bright colors, eating by color is an easy way to load up on nature's superfoods. Each color represents phytochemicals -- compounds that benefit our health in different ways -- which is why you should eat a colorful variety of vegetables. For example, anthocyanins and proanthocyanins -- two antioxidants associated with keeping the heart healthy and the brain functioning optimally -- make foods like blueberries, eggplant and cranberries blue, purple and deep red.

Must Try: 20 Delicious Ways to Color Up Your Diet

The USDA 2010 Dietary Guidelines for Americans, however, suggest paying particular attention to three colors: dark green, red and orange.

Here's how much of each color you should aim to eat every week:

Red and orange vegetables: 5 1/2 to 6 cups each week for most adults

What counts as a cup? 1 large red bell pepper, 8 large strawberries, 12 baby carrots or 2 medium carrots, a sweet potato or a medium pink grapefruit.

Why they’re important: Red foods -- such as tomatoes and red peppers -- contain lycopene, a phytochemical that may help protect against prostate and breast cancers. Alpha and beta carotene make foods like carrots and sweet potatoes so brilliantly orange. The body converts these compounds into the active form of vitamin A, which helps keep your eyes, bones and immune system healthy. These phytochemicals also operate as antioxidants, sweeping up disease-promoting free radicals.

Dark green vegetables: 1 1/2 to 2 cups weekly

What counts as a cup? A cup of cooked greens, 2 cups raw greens or 10 broccoli florets.

Why they’re important: Dark, leafy greens (spinach, chard and arugula) are good sources of lutein and zeaxanthin, phytochemicals that accumulate in the eyes and help prevent age-related macular degeneration, a leading cause of blindness in older people. They’re also rich in beta carotene. Dark green cruciferous vegetables, such as kale and broccoli, provide compounds called indoles and isothiocyanates, which may help prevent cancer by amping up the production of enzymes that clear toxins from the body.

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How many colors did you eat in your last meal?

Brierley's interest in nutrition and food come together in her position as an associate editor at EatingWell. Brierley holds a master's degree in Nutrition Communication from the Friedman School of Nutrition Science and Policy at Tufts University. A Registered Dietitian, she completed her undergraduate degree at the University of Vermont. Related Links from EatingWell: