<p>蓝天白云 and 青天白日 are <strong>idioms</strong>, so they cannot be changed.</p>

<hr>

<p>蓝色 means blue, but 青色 is arguable.</p>

<p>In the colour printing technology, the <strong>jargon</strong> term 青色 is defined to be cyan. However, if you are not talking about the colour printing technology, 青色 can mean blue, cyan, green, or even black.</p>

<blockquote>
  <p>青天白日 blue sky and white sun</p>
  
  <p>绿水青山 green water and green mountains</p>
  
  <p>山青水秀 the mountain is in green, and the water is beautiful</p>
  
  <p>青，取之于蓝，而青于蓝。
  Cyan, is made from blue, but cyaner than blue.</p>
  
  <p>雪青色 violet colour (lit. bluish snow colour)</p>
  
  <p>青草 green grass</p>
  
  <p>青衣 black clothes</p>
  
  <p>青布 black cloth</p>
</blockquote>

<hr>

<p>When does 青 mean blue? When does 青 mean green? When does 青 mean black? There are no rules and no logic for it, just idiomatic. For example, many people use 青草 for “green grass” and therefore 青草 becomes the idiom of “green grass”.</p>

CC BY-SA 4.0
2019-01-17T18:02:54.810Z
2019-01-17T18:15:35.963Z
2019-01-17T18:15:35.963Z
Victor
<p>"青天” normally compare to Non-corrupt officials, can't directly translate to cyan sky.</p>

CC BY-SA 4.0
2019-04-04T16:48:43.440Z
Please develop your answer.
zyy
CC BY-SA 4.0
2019-04-04T02:15:38.363Z
2019-04-04T02:15:38.363Z
will smith
<p>Peole use both 蓝天 and 青天 and I am wondering if there is any difference. While 蓝 means blue, 青 means cyan, right?</p>

<p>Why do people say 蓝天白云 often but seldom 青天白云 (though 青天白日 is sometimes used)?</p>

CC BY-SA 4.0
2019-01-17T19:51:09.363Z
See also: https://www.theworldofchinese.com/2013/06/what-color-is-qing/
青 is not a specific color in natural language (it is "cyan" in painting and publishing domain), more like "a cool/cold hue".
NS.X.
CC BY-SA 4.0
2019-05-29T15:55:33.903Z
[Flag of the ROC](https://en.wikipedia.org/wiki/Flag_of_the_Republic_of_China) - "青天白日滿地紅" ("Blue Sky, White Sun, and a Wholly Red Earth").
Flux
<difference><colors>
If 蓝天 means "blue sky", does 青天 mean "cyan sky"?
# If 蓝天 means "blue sky", does 青天 mean "cyan sky"?

(Asked by: username_0 on 2019-01-17)

Peole use both 蓝天 and 青天 and I am wondering if there is any difference. While 蓝 means blue, 青 means cyan, right?

Why do people say 蓝天白云 often but seldom 青天白云 (though 青天白日 is sometimes used)?

**Tags:** difference, colors

> **Comments:**
> **username_1**: See also: https://www.theworldofchinese.com/2013/06/what-color-is-qing/ 青 is not a specific color in natural language (it is "cyan" in painting and publishing domain), more like "a cool/cold hue".  
> **username_2**: [Flag of the ROC](https://en.wikipedia.org/wiki/Flag_of_the_Republic_of_China) - "青天白日滿地紅" ("Blue Sky, White Sun, and a Wholly Red Earth").  

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## 2 answers

### Answer by username_3 on 2019-01-17. Score: 6

蓝天白云 and 青天白日 are **idioms**, so they cannot be changed.

---

蓝色 means blue, but 青色 is arguable.

In the colour printing technology, the **jargon** term 青色 is defined to be cyan. However, if you are not talking about the colour printing technology, 青色 can mean blue, cyan, green, or even black.

> 青天白日 blue sky and white sun
>
> 绿水青山 green water and green mountains
>
> 山青水秀 the mountain is in green, and the water is beautiful
>
> 青，取之于蓝，而青于蓝。
> Cyan, is made from blue, but cyaner than blue.
>
> 雪青色 violet colour (lit. bluish snow colour)
>
> 青草 green grass
>
> 青衣 black clothes
>
> 青布 black cloth

---

When does 青 mean blue? When does 青 mean green? When does 青 mean black? There are no rules and no logic for it, just idiomatic. For example, many people use 青草 for “green grass” and therefore 青草 becomes the idiom of “green grass”.


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### Answer by username_4 on 2019-04-04. Score: 0

"青天” normally compare to Non-corrupt officials, can't directly translate to cyan sky.

> **Comments:**
> **username_5**: Please develop your answer.  

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