I'm learning Mandarin primarily using Lingodeer and when colors were first introduced I was taught to say “_色的” such as in “月亮是白色的”. Now in Lingodeer I am learning of how to put emphasis on certain words and the example they gave was as follows, “妈妈的头发黑黑的”. Evidently “_色的” is not needed in this situation. Is it simply that “黑” or any other color is an adjective rather than a noun and the purpose of “_色的” is to turn a color into a noun? That's the only thing that comes to mind because I had always interpreted sentences such as “月亮是白色的” to mean "The moon is the color white ('s belonging)".
Ah..I'm not an expert in Chinese language but a native speaker, so the answer is just according to my experience.
Very likely the character "色" could be omitted if you're about to use a word which its most usage is to state a color: white, red, yellow, etc. So the following are both grammatically good:
1. 月亮是白色的 (the moon is of white color) 2. 月亮是白的 (the moon is white)
But when you want to be more accurate, the absence of "色" could cause ambiguity:
1. 剑是青铜色的 (sword is of bronze color) 2. 剑是青铜的 (sword is made of bronze)
What really cannot be omitted is "的". It is "的" that turn a noun into an adjective. We often use "X 是 Y 的" to tell "X is of the property of Y".
I could list some characters that in most cases their usage is to state a color:
红 red 黄 yellow 蓝 blue 黑 black 灰 gray 白 white (also has the meaning in vain, but it's an adverb then) 紫 purple 绿 green
Yes, it is to use the color as a noun that means "a thing possessed of the attribute of appearing with that color". Namely, "白色的" means "a quality-of-whiteness-possessing object" and hence, "月亮是白色的" means "the moon, spoken of poetically, is (是) an object which possesses the quality of white coloration (白色的)".