Short answer
Because the words do not cover the same colours. 23 of the 41 terms in the Colourwise cross-language lexicon either divide a category English treats as one, cover what English separates, or match no single English word, and for each of those a one-word translation is wrong for some of the colours it is used of. The reliable method is to translate from the colour, not from the word: attach a value or a swatch, choose the target-language term that fits that colour and that object, and have a native speaker check the cases near a boundary.
The first is a target language that divides where the source does not. English 'blue' has to become either goluboy or siniy in Russian, and English 'green' either yeondu or chorok in Korean; the English word does not say which. The second is a source term that covers more than any target word: Vietnamese xanh, Welsh glas and Chinese qīng all reach across green and blue, and the text may not say which is meant. The third has nothing to do with colour regions. Japanese ao is the word for blue and also the conventional word for lawns, forests and traffic lights; Hungarian has two words for red whose difference lies in what they are said of. In those cases the colour value is the same and the right word still changes with the object.
When the target language has two terms where English has one, the swatch decides. A light blue is goluboy in Russian, ghalazio in Greek, and azzurro or celeste in Italian depending on the audience; a dark one is siniy, ble or blu. The line is one of lightness, and the studies agree it is not sharp, so a mid blue is the hard case and the one to test on readers. A yellow-green that English would still call green belongs to yeondu in Korean. Where a term's basic status is disputed, as with Turkish lacivert, either word may be acceptable, because most speakers treat the darker term as a kind of the general one. A product range with several blues will need both words in most of these languages.
Going the other way, the translator needs information the word does not carry. For Vietnamese it is usually present: speakers add 'leaf' or 'ocean' to xanh, and a bare xanh in a product listing is a reason to look at the picture. For historical Welsh and Irish the object is the guide, since the dictionaries record glas of grass, of the sea, of eyes, of steel and of grey horses. For Chinese qīng the date and region matter as much as the object: it is a specific blue-green in present-day Mainland usage, a vague green-leaning word for younger speakers in Taiwan, and a wider term in older texts. Where nothing settles it, a hedged rendering such as 'blue-green' is more honest than a confident wrong choice.
A borrowed colour word takes on a range of its own. Himba burou is glossed as blue in the Herero dictionary and names blue, green and purple. The character that writes Mandarin lán, blue, writes the Japanese word for indigo. Japanese has also taken in English 'green' and 'blue' as loanwords alongside midori and ao, and a study of the four found that speakers choose among them by referent. Regional variation inside one language has the same effect: azzurro is the light-to-medium blue for speakers in Verona and only a darker medium blue in Alghero. A glossary built from one region's usage, or from the source language of a loan, will mislabel colours for part of the audience.
Three things travel better than a colour name. A value — HEX for screens, a CIELAB or spectral measurement or a recognised physical reference for goods — fixes the colour whatever it is called. A swatch or photograph beside a neutral reference lets a translator pick the term a native speaker would use. And modified basic terms, 'light greyish blue' or 'dark yellowish green', translate more reliably than evocative ones, because basic terms and modifiers have nearer counterparts across languages than names taken from things; the ISCC-NBS system was built on that principle for English. Evocative names can then be added per market as marketing copy, written fresh for each language and never translated.
| Language | Term | Usually translated | Relation to the English term | What goes wrong |
|---|---|---|---|---|
| Russian | синий (siniy) | blue / dark blue | Splits an English category | Rendering it as plain 'blue' is correct but drops a distinction Russian makes obligatory; a light blue is not siniy. |
| Russian | голубой (goluboy) | light blue / sky blue / blue | Splits an English category | Not a kind of siniy and not interchangeable with it. 'Sky blue' is the nearest English secondary term, but in English that is a shade of blue; in Russian goluboy stands beside siniy as an equal. |
| Modern Greek | μπλε (ble) | blue / dark blue | Splits an English category | Its best example is not the same as that of Russian siniy or Turkish lacivert, so the three 'dark blues' cannot be treated as translations of one another. |
| Modern Greek | γαλάζιο (ghalazio) | light blue / sky blue | Splits an English category | Thierry and colleagues (2009) found Greek speakers' brain responses distinguished the two blues more strongly than English speakers' did; that is a measured difference in automatic processing, not evidence that English speakers cannot see the difference. |
| Italian | blu | blue / dark blue | Splits an English category | English 'blue' is wider. A mid or light blue translated into Italian as blu will read as too dark a word. |
| Italian | azzurro | light blue / blue / azure | Splits an English category | The English cognate 'azure' is a literary word for a bright sky colour and is not an everyday equivalent. |
| Italian | celeste | light blue / sky blue | Splits an English category | Whether it is basic, and how much of the light-blue range it takes from azzurro, depends on the region. A national audience will not read it uniformly. |
| Japanese | 水 (mizu) | light blue | Splits an English category | English 'light blue' is a compound understood as a kind of blue. For most speakers in the 2017 sample mizu is a category of its own. |
| Japanese | 紺 (kon) | navy blue / dark blue | Splits an English category | Colourwise links it to 'navy' as the nearest English lexicon term; that link is editorial. The study compared naming categories and did not test English navy against kon. |
| Mandarin Chinese | 青 (qīng) | green / blue / cyan / blue-green | No single equivalent | No single English word fits. The right rendering depends on the date and origin of the text and often on the object described; a fixed gloss of 'blue' or 'green' will be wrong in a share of cases. |
| Korean | 연두 (yeondu) | yellow-green / light green | Splits an English category | The same research group measured discrimination thresholds and found them no different between Korean and English speakers. The boundary affects speeded judgements, not what can be told apart. |
| Korean | 초록 (chorok) | green | Splits an English category | English 'green' is wider. A yellow-green translated as chorok names the wrong category for a Korean reader. |
| Vietnamese | xanh | green / blue | Merges English categories | A lone xanh cannot be translated without context. The speaker is not being vague: Vietnamese puts the distinction in a modifier where English puts it in the head word. |
| Welsh | glas | blue | Merges English categories | 'Blue' is the usual modern translation, but in older texts, place names and fixed expressions glas may be green or grey. A historical dictionary shows the range the word has had; it does not show how often each sense is used today. |
| Irish (Old and Middle Irish) | glas | green / grey / blue | Merges English categories | The English word depends on the thing described: green for foliage, grey for a horse or stone, blue or grey for eyes. The record describes medieval Irish, not present-day usage. |
| Dani | mili | dark / black | Merges English categories | 'Black' and 'dark' are both poor glosses: the term is defined by coolness as well as darkness. A two-term vocabulary names colours broadly; it is not a report that only two colours are seen. |
| Dani | mola | light / white | Merges English categories | 'White' and 'light' are both poor glosses: the term takes in saturated warm colours such as red. It did not fit Berlin and Kay's first description of a two-term language, which had to be revised. |
| Berinmo | nol | green / blue | Merges English categories | No English word covers it, and it is not English green plus English blue: its edge with wor cuts through green. See the language record for the dispute about what the experiments show. |
| Berinmo | wor | yellow | Merges English categories | 'Yellow' leaves out most of what the term covers. A leaf-green sample may be wor where an English speaker expects it to group with the other greens. |
| Himba (a variety of Herero) | dumbu | yellow / beige | Merges English categories | Neither 'yellow' nor 'beige' conveys its extent. The study's finding is about where a boundary falls, not about failing to see green. |
| Himba (a variety of Herero) | burou | blue | Merges English categories | The Herero dictionary's 'blue' is too narrow for Himba usage. A loanword's meaning in the borrowing language cannot be read off the language it came from. |
| Tsimane' | shandyes | green | Merges English categories | The published gloss '~green' marks the most frequent use, not an equivalence. For a monolingual speaker it may equally be said of a blue thing. |
| Tsimane' | yụshñus | blue | Merges English categories | The published gloss '~blue' marks the most frequent use. Two interchangeable words for one category are not the same as one word, and neither is a separate blue for monolinguals. |
Why: Filter labels were translated one-to-one, so a single English 'blue' facet became the dark-blue word in a language with two blues.
Fix: Build facets per language from the colour values of the products, and let a language with two blues have two facets.
Why: The source word covered several target-language categories and the translator chose without seeing the item.
Fix: Send the swatch or reference value with the text, and translate the colour last.
Why: Evocative token names were translated, and each translation suggests a slightly different colour.
Fix: Keep token names language-neutral (role or scale step) and localise only the user-facing label.
Why: The word's range has narrowed since the text was written.
Fix: Use a historical dictionary with dated citations for the period, and translate by the object described.
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.
Colourwise analysisLimited evidence
23 of 41 terms in the Colourwise cross-language lexicon are classified as splitting an English category, merging English categories or having no single English equivalent.
Based on: Count of records by the equivalence class Colourwise assigned, each record resting on the sources it cites.
Caveat: The lexicon favours terms studied because they differ from English; most everyday colour words in most language pairs translate without trouble.
Source: Basic colour terms in Modern Greek: Twelve terms including two blues (Androulaki and colleagues, Journal of Greek Linguistics 7: 3–47, 2006); Differences in color naming and color salience in Vietnamese and English (Color Research & Application 28: 113–138, 2003); Geiriadur Prifysgol Cymru: A Dictionary of the Welsh Language (entries glas, gwyrdd, llwyd); Color categories: evidence for the cultural relativity hypothesis (Cognitive Psychology 50: 378–411, 2005)
FactModerate evidence
Japanese ao, usually given in bilingual dictionaries as 'blue', is also used of lawns, forests, traffic lights, unripe tomatoes and green apples.
Source: Searching for the semantic boundaries of the Japanese colour term 'ao' (doctoral thesis, 2005)
FactModerate evidence· Verona and Alghero, Italy
Italian azzurro denotes medium and light blue for participants in Verona, while participants in Alghero used mostly celeste for that range and kept azzurro for a darker medium blue.
Caveat: Two locations; other regions were not sampled in this study.
FactModerate evidence
Monolingual Vietnamese speakers relied more on multi-word colour names, and monolingual English speakers more on single basic and object-derived words, when naming the same 110 samples freely.
ConventionModerate evidence
Describing a colour with a basic term and standard modifiers is a naming convention designed to communicate more reliably than names borrowed from things.
Caveat: The ISCC-NBS method was designed for English; that modified basic terms translate more reliably is Colourwise's inference, not a tested result.
Reviewed 1 October 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.