usage - Is there a difference between 赤{あか} and 赤色{あかいろ}?

While studying Japanese I've met some problems with distinguishing some vocabulary.

For example we have:

• 赤{あか} = Red (color)


• 赤{あか}い = Red (adjective)

But what about 赤色{あかいろ}? Is there a difference between that and 赤{あか}?

Is the former just there in order to study the Kanji, or are there differences in usage (and maybe "acception") between the two?

I suspect it's the second, but it would be nice to have a good explanation about it.

Answer

1. 
   

   I think the same difference applies in English i.e. "red" versus "red colour".

   
   

   "red colour" forces you to perceive it as a colour, while "red" has no such limitation.

   
   
   

   This means "red" can be used symbolically to represent other things. (Much like how "white" is to "purity", and "green" is to "environment" etc.)

   
   

   This means 赤{あか} and 赤{あか}い can be used symbolically, while 赤{あか}色{いろ} forces you to perceive a colour (less likely to be perceived symbolically).

   
   


2. 
   

   From a grammar standpoint,

   
   
   
   
   • 
     

     赤{あか}月{つき}(red moon) is a noun on its own.

     
     
   
   
   • 
     
     

     赤{あか}い月{つき} is the noun 月{つき} modified by the adjective 赤{あか}い.

     
     
   
   
   • 
     

     赤色{あかいろ}の月{つき} is the noun 月{つき} modified by the noun 赤色{あかいろ} via the genitive case¹ particle `の

     
     
   
   
   
   

   Semantically I see no difference.

   
   


3. 
   

   This is my conjecture: Using "red" means that the object is being inherently red or has "red" as an intrinsic quality; and "red colour" implying that the object is not inherently red or does not have "red" as an intrinsic quality.

   
   
   

   EDIT: There are compound nouns that are of the form 赤～ such as:

   
   

   
   

   赤{あか}狼{おおかみ} - Red wolf

   
   

   赤{あか}蕪{かぶ} - Red turnip

   
   

   赤{あか}狩{が}り - Communist hunting, red-baiting (Harassment or persecution (of someone) on account of known or suspected communist sympathies.)

   
   

   
   

   This leads me to conjecture that things that are inherently red in colour or are closely associated with the colour red or the concept of "red" (see point 1.) can have compound nouns that are formed by 赤+[noun] (First bullet of point 2.) And things that are not take on the 赤い+[noun] structure (Second bullet of point 2.).

   
   

   Also consider why "Red carpet" takes on the 赤い+[noun] construction: 赤いじゅうたん even though it feels like a complete noun on its own. Carpets do not have to be inherently red, the colour is incidental.

   
   

   So this leads me to conclude that if the colour (or its related symbolic concept) can be incidental, 赤い+[noun] is used. If it is not incidental then it is quite likely that 赤+[noun] will be an acceptable word.

   
   

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1: Genitive Case: It is the grammatical case that marks a noun as modifying another noun. A genitive construction involves two nouns - the head (modified) noun and the modifier noun. The modifier noun modifies the head noun by expressing some property of it.