Why is red wine red?

Here's a fun fact that surprises most people: squeeze a red grape, and the juice that comes out is clear. Almost no grapes have red flesh — the colour is all in the skins. Red wine is red because the winemaker lets the clear juice sit with those dark skins long enough to extract their pigments.

The pigments responsible are called anthocyanins — the same compounds that make blueberries blue, cherries red, and aubergines purple. In grapes, they're concentrated in the outer cell layers of the skin. The main one is malvidin-3-glucoside, which makes up 40-90% of a grape's total anthocyanins.

Different grapes have different amounts of these pigments, which is why some red wines are deep purple and others are pale ruby. Cabernet Sauvignon, Syrah, and Malbec are packed with anthocyanins (400-800 mg/L), producing inky wines. Pinot Noir and Nebbiolo have much less (200-400 mg/L), giving lighter, more translucent reds.

The extraction process — called maceration — is where the winemaker controls colour intensity. More skin contact time = deeper colour. Higher temperature = faster extraction. Most red wines macerate for 1-4 weeks. Rosé wine uses the same grapes but limits skin contact to just a few hours, extracting only a blush of pink.

As red wine ages, the colour story gets interesting. Young wines are purple-red because they're full of free anthocyanins. Over years, these molecules link up with tannins to form bigger, more stable but less vibrant pigment complexes. The wine gradually shifts from purple to ruby to garnet to brick-orange — a visual timeline of its age. Eventually, very old wines can look almost brown. This is perfectly natural and a sign of graceful ageing, not a fault.

This science also explains Champagne's 'Blanc de Noirs' style: press Pinot Noir grapes quickly and gently, without any skin contact, and you get clear juice for white sparkling wine. It's proof that grape colour and juice colour are completely separate things.