Red wine is necessarily made from black grape varieties because the colour is extracted from the grape skins. Sometimes, a small amount of white grapes may also be used in the blend, but they only contribute to the aroma and flavour of the wine. If they were prevalent, they would tend to dilute the colour to the point it would result in a rosé, not a red, wine. Therefore, the true characteristic of red wines is the use of whole black grapes. During fermentation, the pigment is extracted from the skins and seeps into the liquid. In addition to the pigment, other substances are also extracted from the skins: the polyphenols, among which are the tannins. Tannins are also extracted from the grape seeds. Therefore, red wine is different from white wine, not only in colour, but also for the presence of more substances that make it fuller-bodied and sometimes astringent.

Tannins are responsible for the sense of astringency on the palate—that sensation of dryness on the gums—because they bind to the proteins in saliva which reduces the lubricant effect. In a wine’s balance, this sensation is not problematic, but it is amplified at low temperatures. This is the reason why red wines are never served too chilled. The colour of a red wine can vary from a violet hue in younger wines, through ruby- and garnet red and up to brick red in highly aged wines.The most common black grape varieties throughout the world are Cabernet, Merlot, Grenache, Pinot Noir, Tempranillo, Carménère, and Malbec. In Italy, every region has its own native grape varieties, the most common black grape varieties are Sangiovese, Barbera, Montepulciano, Primitivo, Nebbiolo, Aglianico, Dolcetto, and Nebbiolo.