The short answer is that the skin of the grapes gives the wine its color. When a grape is pressed the juice itself is clear or white. This is true of nearly every variety of grape. The pigments, or the substance present in plants (and animals) that gives it color, of grapes are in their skins. As the juice ferments the skins of the grapes shed pigments and give the wine its red color. The red colors vary from light red to ruby to maroon, garnet, almost black and nearly every shade in between.

If you press grapes and ferment the juice without the skins you end up with a white wine, even from red grapes. A white wine made from red grapes is called a blanc de noir. If you leave the skins in contact with the juice for a brief period of time the wine is only slightly colored and called a blush or rose’ (a term that has fallen out of use of late.)

Most red wines are of the varieties, Pinot Noir, Zinfandel, Merlot, Shiraz, Syrah, Cabernet Franc, Petite Sirah, Shiraz, Sangiovese, Malbec, Grenache, Pinot Noir, and Cabernet Sauvignon.