Color May Be Key to Nutrition
The pigmentation in fruits and vegetables is directly related to phytochemical content. Phytochemical content is what make the fruits and vegetables nutritious.
Foods higher in colors such as reds, purples, blues and greens are generally better for you. This is why buying fruit that is vine ripened is better for you. Darker fruits and vegetables are more nutritious because in theory without the color the phytochemicals are not there.
U.S. Dept. of Agriculture Human Nutrition Research Center at Tufts University in Medford, MS.