DEAR DR. BLONZ >> There was an animated discussion about the roles of fruit and vegetable colors at a recent party. One issue was whether the darker the color, the healthier the food. Another issue was about the color of oranges and whether those with some green should be expected to be less ripe and sweet than the all-orange ones. I was hoping that you could help out.

— S.T., St. Louis, M issouri

DEAR S.T. >> Nature has a kinship with color; it’s one of her most important forms of communication. As the saying goes, “We eat first with our eyes.” The presence (or absence) of specific colors is seen as an indicator of wholesomeness or ripeness and a hint of flavors and textures.

Although colors are a primary language in nature, darker colors do not have the final word on health. Lighter-colored foods can be just as rich in nutrients as darker ones, supporting the stance that it is important to include all colors of whole foods in your diet to receive a wide range of nutrients and beneficial phytochemicals.

Regarding oranges, some fruits, such as bananas or stone fruits, contain enzymes that break down their complex carbohydrates into simple, sweeter-tasting sugars, and these remain active after harvest. (Colors can also be affected by this ripening process.) However, this is not the case with oranges, which are traditionally harvested at the peak of ripeness. When it is picked, the orange is about as sweet as it’s going to be, and its vitamin C content will be at its peak.

Don’t look to an orange’s color as an indication of its ripeness; they can “regreen,” a process unrelated to ripeness or taste. The color is more a reflection of the temperature before harvest than of the flavors and sugars inside. Also, there is no reason to save an orange in the hopes it will improve in flavor or nutrient value as it sits.

Finally, as a colorful side note, studies have revealed that people can have difficulty with food when the colors are wrong. One study reported that volunteers couldn’t correctly identify genuine strawberry flavoring when it was tinted green. And, in a classic work on colors, a group in the early 1970s was fed a meal of steak, peas and French fries, but under lighting that concealed their appearance. At the meal’s end, the room lights were raised to reveal a blue steak, red peas and green French fries. Irrespective of being informed before the study that all food was wholesome and that the colors were a result of added tinting, several volunteers became ill.

Kensington resident Ed Blonz has a PhD in nutrition from UC Davis. Email him at cctimes@blonz.com.