What primarily determines the richness of a wine's color?

The richness of a wine's color is primarily influenced by the type of grape used. Different grape varieties have varying skin thicknesses and colors, which contribute significantly to the final hue of the wine. For instance, red wines typically come from grapes with thicker skins that impart more color during fermentation, while white wines are made from grapes with less pigmentation.

The skin of the grape contains anthocyanins, which are natural pigments that give red wines their distinctive colors. Thus, the specific variety of grape plays a crucial role in determining not only the color but also the overall character and flavor profile of the wine. In this context, while other factors like sugar levels, tannins, or glycerin can influence aspects of the wine, they do not primarily dictate its color.