The three key factors to consider when grading a wine are taste, aroma, and color, and the color aspect makes more of a difference than you may know. While white wines are simpler to produce and review, they skip this one important step that makes red wines red.

You cannot produce red wine from white grapes, as red and purple grapes have polyphenols that are crucial to make red wine. Anthocyanin is the main one found in dark grapes, and red wine gets its color from these anthocyanin pigments, tannins, and flavonoids that originate or develop in the skin of the grapes during the fermentation process.

While it's primarily the anthocyanin that contributes to the reddish hue of red wine, other factors like the pH, age, and growing conditions of the grapes can come into play. The longer a wine is aged, the bluer its color will be, and red wines with a lower pH tend to be redder, while those with lower acidity will have a purplish hue and be sweeter red wines.