Short answer
Colour is a good guide to ripeness in many fruits, because ripening replaces chlorophyll with carotenoids or anthocyanins on a fairly predictable schedule. It is a poor guide to freshness and no guide at all to safety. Harmful bacteria can grow without changing how food looks, and harmless reactions such as oxidation or enzymatic browning change colour without making food unsafe. Use dates, storage, smell and, for cooked meat, a thermometer — never colour alone.
Ripening is a coordinated programme. In climacteric fruits such as bananas, tomatoes, mangoes and apples a burst of ethylene triggers softening, sugar accumulation, aroma and colour change together. The chlorophyll-containing chloroplasts are converted into carotenoid-rich chromoplasts, so green gives way to yellow, orange or red; some fruits also make anthocyanins in the skin. Because the colour change is driven by the same signal as sweetness and softening, it is a reasonable proxy for eating quality in these fruits.
Some fruits change colour without ripening further, or ripen without changing colour. Non-climacteric fruits such as citrus and grapes do not continue to ripen after picking, so colour at the shop reflects picking time. Citrus grown in warm climates can be ripe inside while the peel is still partly green, because peel colour responds to temperature as well as maturity. Apple skin colour depends heavily on sun exposure and variety.
Some spoilage is visible: mould colonies, slime, green or grey discolouration in cured meats, dark soft patches on fruit. But visible change usually comes late, and many changes that look like spoilage are not. Brown metmyoglobin on the surface of a steak, a brown cut apple, a greyish hard-boiled egg yolk and the olive colour of cooked greens are all chemistry, not contamination. The opposite error is more dangerous: food carrying pathogenic bacteria can look, smell and taste completely normal. Colour cannot tell you food is safe.
Retail lighting is often chosen to flatter: warm, red-rich light makes meat look redder and bread more golden; some fresh-produce displays use lamps that enhance greens and reds. At home, under a different spectrum, the same product can look duller or more brown. Judging produce by colour works best in daylight or under high-quality neutral lighting, and comparing like with like in the same light.
Why: Oxymyoglobin converts to metmyoglobin with time and low oxygen in the pack or fridge.
Fix: Judge by use-by date and storage, not colour.
Why: Warm growing conditions left chlorophyll in a ripe peel.
Fix: Judge citrus by weight and aroma rather than skin colour.
Why: Display lighting with a spectrum chosen to flatter reds or greens.
Fix: Compare under daylight before deciding the product has deteriorated.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactStrong evidence
In climacteric fruits, ripening is coordinated by ethylene and includes chlorophyll degradation and accumulation of carotenoids and, in some species, anthocyanins.
Source: Molecular and Hormonal Mechanisms Regulating Fleshy Fruit Ripening; Fruit ripening: dynamics and integrated analysis of carotenoids and anthocyanins
FactModerate evidence
Colour is an unreliable indicator of whether meat has been cooked to a safe temperature; premature browning and persistent pinkness occur independently of internal temperature.
Colourwise interpretationModerate evidence
Colour is never sufficient evidence that food is safe to eat: many colour changes are harmless chemistry, and contamination with pathogens is often invisible.
Based on: Colourwise's position, drawn from the pigment and browning chemistry on this pillar and from meat-science guidance that colour does not track doneness.
Colourwise interpretationModerate evidence
Retail and home lighting with different spectra can change how red, green or brown food appears, so colour judgements made under one light may not transfer to another.
Based on: Follows from illuminant metamerism and colour rendering as covered in the lighting pillar; not a measurement of any particular food display.
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.