"Green apple"

Translation: 녹색 사과

[parisandsky]

Why is 초록 not acceptable when its in the list of translations?

[LucyApril]

Usually these are used with 색/색인 to form modifiers in a sentence.

[Ash-Fred]

초록 사과 is now accepted.

[Soccermom98]

Why in some of these lessons when the color is used to describe a noun is 인 not used?

[Ash-Fred]

It's just like chocolate milk. 초록색인 사과 or milk made with chocolate is not incorrect, but we prefer having the two nouns by themselves for the sake of brevity.

[sylmina]

Why 초록 doesn't count?

[Ash-Fred]

초록 사과 is now accepted.

[91blossom]

초록(+색), 보라(+색)/녹(+색)

[LiKenun]

The pattern I've noticed is that a noun is preceded by an adjective (프른, 노란, 빨간) or color+색. In the latter case, the color is in noun form, but it's a noun being used to describe another noun.