The color of red wine derives from the interaction of grape skins with fermenting juice; particularly, from anthocyanins, pigments contained in grape skins.
Some winemakers (usually of bulk wines, though not necessarily) may also use artificial procedures to improve the natural color of wines.
Around 75 legally authorized chemicals are utilized to control wine in the United States, including filtration & preservative treatments as well as compounds that target consistency and color.
How can you know whether the wine you are going to purchase has been tinted artificially? And how concerned should you be?
If your tongue or teeth appear purple after drinking red wine, this does not always indicate the usage of artificial colorants. Red wine may accomplish this naturally.
Certain colorants are required by law to be listed on the wine label. Carmine and cochineal extracts are examples of this. So look for them.
Some colorants, such as Mega Red and Mega Purple, are derived from grape juice concentrates and do not need to be stated on wine labels.
It's tough to know which wineries are using them. Their usage may appear nasty, yet there have been no recorded health consequences.
Food dyes are used for the same reason. It seems that people like colors with a certain depth and intensity.