Short answer
Both come from the same leaf. Black tea is made by bruising the leaves and letting their own polyphenol oxidase oxidise catechins into theaflavins, which are orange-red and bright, and thearubigins, which are red-brown and give depth. Green tea is heated soon after picking to destroy that enzyme, so the catechins stay largely unoxidised and the infusion stays pale. The balance of theaflavins and thearubigins is what tea tasters judge as brightness and colour.
Fresh tea leaves are rich in catechins, colourless polyphenols, and in the enzyme polyphenol oxidase. Black tea makers wither, roll or crush the leaves to break cells and then let them oxidise — a step still called fermentation although no microbes are involved. Oolongs are partly oxidised. For green tea, the leaves are steamed (the Japanese tradition) or pan-fired (the Chinese tradition) soon after picking, which denatures the enzyme and fixes the leaf close to its fresh chemistry. The colour difference in the cup is a direct record of how far enzymatic oxidation was allowed to run.
When catechins are oxidised in pairs they form theaflavins, relatively small molecules that give black tea its bright orange-red and its brisk, astringent character. Further oxidation and polymerisation produce thearubigins, a large and poorly defined family of red-brown compounds that give body and depth of colour. Tea tasters score liquors for brightness, briskness, strength and colour, and studies of commercial black teas find these scores track theaflavin and thearubigin content. A tea high in theaflavins looks bright and coppery; one dominated by thearubigins looks dull and dark.
Tea pigments are sensitive to their surroundings. Lemon juice lightens black tea noticeably, a sign that some of its coloured polyphenols respond to acidity much as anthocyanins do. Hard, alkaline water deepens and dulls it, and can leave a film on the surface as polyphenols bind calcium and oxidise. Milk scatters light and its proteins bind polyphenols, turning red-brown into the familiar tan. Green tea left to stand, or kept warm, gradually turns from yellow-green to yellow-brown as its catechins oxidise without the enzyme.
The same tea looks different in soft and hard water areas; the change is chemistry, not a difference in the leaf.
In the tea trade, liquor colour is assessed alongside the infused leaf, and bright, clear colour is prized in black teas meant for blending. Colour is a reasonable cue to processing but a weak cue to flavour on its own: two teas of similar colour can taste very different, and deep colour can come from over-oxidised or poorly stored leaf as easily as from good processing. As with every food colour on this pillar, it says nothing about safety.
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.
FactModerate evidence
Theaflavins and thearubigins are formed by enzymatic oxidation of catechins and their gallates during the oxidation stage of black tea processing, and are largely responsible for its briskness, brightness, strength and colour.
Source: Spatial variability of theaflavins and thearubigins fractions and their impact on black tea quality
FactLimited evidence
Thearubigins contribute about 35% of the total colour of black tea liquor.
Caveat: A figure quoted from earlier literature in one study of CTC teas; the share varies with tea type and processing.
Source: Spatial variability of theaflavins and thearubigins fractions and their impact on black tea quality
FactModerate evidence
The enzymatic browning chemistry that makes black tea is the same polyphenol oxidase reaction that browns cut fruit, deliberately allowed to run.
Source: Prevention of Enzymatic Browning by Natural Extracts and Genome-Editing: A Review on Recent Progress; Spatial variability of theaflavins and thearubigins fractions and their impact on black tea quality
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.