Anthocyanins are responsible for the colour of red wine and the pigmentation comes primarily from the skin of the grape. Long contact between the fermenting grape skin and the juice extracts the colour and other polyphenols from the skin. The higher the alcohol the easier it is for the colour to leech from the skins.
After the wine is created the anthocyanins in the wine typically make red wines with a blue hue. However as the wine ages the anthocyanins start to join together. Eventually the long chains become too big and the anthocyanins precipitate out. Initially the blue anthocyanins precipitate first. This causes young blue wine to fade into a garnet colour before the red falls out leaving a very mature tawny colour.