The Green Tea Palette: Chlorophyll and Flavonoids
Unoxidised green teas owe their colour primarily to chlorophyll a (blue-green, peak absorption ~665nm) and chlorophyll b (yellow-green, ~645nm). Together they produce the characteristic jade-green colour of high-quality Chinese greens and the more vivid emerald of steamed Japanese sencha. As noted in our guide to chlorophyll in tea, shade-grown teas like gyokuro and matcha have dramatically higher chlorophyll concentrations, producing a deeper, more saturated green.
In the brewed cup, green tea colour is modified by flavonoid compounds — primarily quercetin and its glycosides — which absorb violet and blue light and transmit yellow. The interplay of chlorophyll green and flavonoid yellow produces the diverse green-gold palette of different green teas. Longjing (pan-fired) loses more chlorophyll to heat-blanching and appears more yellow-green; sencha (steamed) retains more chlorophyll and appears more vividly jade-green.
🧠 Expert Tip: Colour as Quality Check
A fresh, well-processed green tea should brew to a bright, clear colour. Murky, brown, or olive-drab liquor indicates poor processing (insufficient kill-green), old stock (chlorophyll degraded to phaeophytin), or water too hot (chlorophyll destroyed during brewing). The colour tells you before you taste whether the tea is worth drinking.
Black Tea's Colour: Theaflavins and Thearubigins
The colour chemistry of black tea is entirely different from green tea — it is dominated by polyphenol oxidation products rather than photosynthetic pigments. During the oxidation stage, polyphenol oxidase converts catechins to benzo-tropolone compounds (theaflavins, TF) and then to much larger polymeric compounds called thearubigins (TR).
| Compound | Colour | % in dry black tea | Contributes to | Stability |
|---|---|---|---|---|
| Theaflavin-1 | Bright orange-red | 0.5–1.5% | Brightness, "briskness" | Moderate |
| Theaflavin-2a, 2b | Orange-red | 0.5–1.5% | Colour intensity | Moderate |
| Theaflavin-3 | Deep orange | 0.3–1.0% | Depth of colour | Lower |
| Thearubigins | Dark brown-red | 15–20% | Body, depth, "cream" | Higher |
| Theabrownins | Near-black | Variable | Very dark aged teas | Very stable |
The ratio of theaflavins to thearubigins determines the visual quality of the brew. Teas with a high TF:TR ratio appear brighter and more orange-amber, with greater clarity. Those dominated by thearubigins appear darker, more opaque, and less vibrant. Premium single-estate teas optimised for flavour often have better TF:TR ratios than mass-market blends, which is why high-quality Darjeeling has a distinctive brightness that a cheap tea bag cannot match.
Anthocyanins: Purple and Red Specialty Teas
Anthocyanins are flavonoid pigments responsible for the red, purple, and blue colours of many fruits, flowers, and vegetables. A small number of tea cultivars have been bred or selected to accumulate unusually high anthocyanin levels — particularly in growing conditions with high UV exposure and certain soil conditions.
Zi Juan (Purple Bamboo) from Yunnan, Taiwan's indigenous purple oolong, and several African specialty teas contain significant anthocyanins that turn the brewed tea a striking purple-red. Notably, anthocyanins are pH indicators — they are redder in acidic conditions and bluer in alkaline. Adding lemon juice to a purple tea instantly intensifies its red colour; adding alkaline water turns it grey-purple. This visual demonstration of pH chemistry is one of the more spectacular effects in tea brewing.
Pu-erh: The Dark Universe
Aged and fermented pu-erh teas have a colour that no other tea type approaches — a deep, dark reddish-brown to near-black, often with a syrupy opacity in overbrewed cups. This extreme dark colour comes from theabrownins: loosely characterised, very high-molecular-weight polyphenol oxidation polymers produced by the prolonged microbial activity of pu-erh fermentation and storage.
Theabrownins are structurally distinct from thearubigins (which are produced purely enzymatically in black tea) and currently poorly characterised — they represent some of the most scientifically complex material in all of food chemistry. Their dark colour, bitter-astringent taste at high concentrations, and potential health effects (including observed lipid-lowering properties in some animal studies) make them a significant ongoing research interest.
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