Why red wine is red

Quick answer

Red wine is red mainly because coloured grape skins are kept in contact with the juice during winemaking. The skins contain anthocyanins—natural pigments that dissolve into the juice during maceration, the period when juice or fermenting wine remains with grape solids.

Most red grapes have dark skins but pale or lightly coloured flesh. Crushing the grapes therefore releases mostly pale juice. It is the time spent with the skins, usually during alcoholic fermentation, that gives the wine its red, purple or ruby appearance.

The final colour depends on more than the grape’s skin. Variety, ripeness, pigment concentration, acidity, skin condition, contact time, temperature, cap management, pressing, oxygen exposure and ageing can all affect the result. These factors interact, so no single winemaking decision guarantees a particular shade.

The colour is mainly in the skins

Grape skin and grape flesh do different jobs. In most red wine grapes, the skin contains much more colour than the pulp. The pulp produces pale juice, even when the outside of the grape looks almost black.

The main pigments are anthocyanins. They are a group of natural, water-soluble compounds found particularly in the skins of dark-coloured grapes. In young red wine, they provide much of the visible purple, violet, ruby or red colour.

This is why a red grape does not automatically produce red wine. If its juice is separated quickly from the skins, there may be little opportunity for anthocyanins to enter the liquid. The same principle helps explain why some wines made from red grapes can be pale.

How colour moves into the wine

The process begins when grapes are crushed. Crushing releases juice and breaks some of the grape structure, allowing the liquid to come into contact with skins, seeds and sometimes stems.

The next stage is often called maceration. This is the contact between juice or fermenting wine and grape solids. During maceration, compounds move from the skins and seeds into the liquid. This movement is called extraction.

In typical red-wine production, alcoholic fermentation commonly takes place while the skins and seeds are still present. Fermentation is the microbial conversion of grape sugars into alcohol and other products. It is not the same as maceration, but the two processes can happen at the same time.

Winemakers may manage the grape solids in different ways. Moving liquid over the floating skins, controlling contact time and deciding when to press the wine all influence which compounds are extracted. Temperature, alcohol development and the condition of the fruit also matter.

These are influences rather than fixed recipes. Longer skin contact can affect colour, but it does not always create a proportionally darker or more stable wine. Pigments and tannins do not all extract or evolve in exactly the same way.

Colour and tannin are connected—but different

Anthocyanins are colour pigments. Tannins are different phenolic compounds associated particularly with astringency, bitterness and structure. They can come from grape skins and seeds, as well as from oak in some wines.

Both pigments and tannins may come from the same grape solids, which is why colour and tannin are sometimes discussed together. Tannins can also interact with anthocyanins and contribute to more stable forms of colour as the wine develops.

But tannin is not what primarily makes young red wine red. A deeply coloured wine is not automatically high in tannin, and a lighter-coloured wine is not automatically soft or low in tannin.

Phenolics is the broader term for this family of plant compounds. It includes anthocyanins, tannins and other substances involved in colour, bitterness, astringency and mouthfeel.

Why red wines have different shades

A young red wine may look purple, violet or ruby. As it matures, its colour can move towards garnet, red-orange or brick tones. This happens as original anthocyanins change and react with other wine compounds. Oxygen exposure and ageing can contribute to the formation of new, more stable pigment forms.

Acidity also affects how anthocyanin colour is expressed. The same broad group of pigments can appear different depending on the wine’s pH and chemical environment. That does not mean a simple rule such as “more acidity always means darker wine”; colour is shaped by several interacting factors.

Grape varieties also differ in their colour potential. Australian drinkers may encounter red wines made from Shiraz, Cabernet Sauvignon and Pinot Noir. Shiraz is the common Australian name for the variety also known internationally as Syrah. These varieties can differ in their pigment potential, but the finished colour also depends on growing conditions and winemaking. No variety has one guaranteed colour profile.

A quick comparison with rosé and white wine

Rosé is generally lighter because the juice has less contact with dark grape skins than a typical red wine. Limited or gentler contact usually means less colour extraction, although rosé can be made in different ways.

The skin colour of a grape also does not determine the wine’s colour by itself. Red-grape juice can produce a pale wine when it is separated from the skins before substantial pigment extraction. This is a useful reminder that the juice and the skin are not the same colour.

What colour does not tell you

Look at colour as one part of tasting, not as a complete verdict. A darker red wine is not automatically:

• sweeter;
• higher in alcohol;
• fuller-bodied;
• stronger;
• older; or
• better quality.

Colour may reflect grape composition, skin contact and pigment chemistry, but it is not a direct measurement of these other qualities. To understand the wine, you still need to smell and taste it.

Common questions

Does darker red wine mean it has more tannin?

Not necessarily. Colour and tannin can be extracted from the same grape solids and may interact, but they are different compounds and do not always increase together.

Does longer maceration always make wine darker?

No. Longer contact can influence extraction, but the result depends on temperature, fruit condition, alcohol, pressing, pigment stability and other factors.

Why can an older red wine look brick-coloured?

Ageing changes the original pigments and encourages new pigment forms to develop. This can shift a wine from youthful purple or ruby towards garnet or brick, but colour is not a reliable age calculator.

Is Shiraz always darker than Pinot Noir?

No. Shiraz and Pinot Noir are useful Australian examples of red varieties, but variety alone does not determine the final colour. Growing conditions and winemaking choices also matter.