First, why are green grapes called white? Because the juice (and, by extension, the wine) is more white than green.
What is the difference? Apparently red grapes are more awesome than white grapes in, almost, every way:
The reddish-black color of red grapes is due to the presence of flavonoids, an antioxidant. Red grapes are rich in vitamins, especially vitamin C and B, copper, anthocyanins, manganese and potassium. It is also low in calories and high in dietary fiber. A cup of red grapes has around 61 calories which makes it an ideal snack, especially for those looking to lose weight.
Green grapes which are also known as white grapes are available year-round. It is rich in carbohydrates, vitamin C and vitamin K. Green grapes are low in calories, saturated fat and sodium and has zero cholesterol. It contains flavan-3-ols, an antioxidant. Some amount of iron and potassium are also found in green grapes.
Most nutritionists and health experts would recommend consuming more of red grapes. The reason for this would be the high content of antioxidant resveratrol in red grapes, as compared to green ones.
Red grapes contain anthocyanins, a polyphenol, which is absent in white grapes. It is the presence of anthocyanins, which gives red grapes its characteristic color. Anthocyanins are absent in green grapes.
The phenolic content of red grapes is higher than that of green grapes. This is because of the high anthocyanin content in red grapes. Since green grapes do not have this compound, therefore its total phenolic content is low.
Red grapes also contain syringetin, syringetin 3-O-galactoside, laricitrin and laricitrin 3-O-galactoside, which are a class of flavonoids. These flavonoids are absent in green grapes.
Red grapes have a higher level of oxalates than green grapes. High levels of oxalate can contribute to the formation of kidney stones.The polyphenolic, flavan-3-ols is higher in green grapes than in red grapes.The flavonol myricetin is only found in red grapes.
Now, what is the “French Paradox”? The French have a much less risk of heart attack even though they consume an above-average level of fat. It is believed that this is due to their red wine intake.