"고양이의 색깔은 노랑이에요."
Translation:The cat's color is yellow.
노랗다 (노라요/노란) is an adjective, while 노랑 is a noun. Some languages don't have this distinction (in English yellow is yellow, period), while some do (Polish: żółty/żółć). Same goes with 파랗다/파랑, 빨갛다/빨강, 하얗다/하양, 검다/검정 for blue, red, white and black. I think I listed them all
Hi Staszek: True. I tried to answer Bb5's query though I am still quite unsure about the origin of those color words.
Using the usual verb -nominalization process, the color nouns should logically end with either 기 or 음/ㅁ. This "ㅇ"- nominalization is definitely an irregularity. It has been suggested that it originates from the babification of 음/ㅁ (corruption of sound?) but there is nothing to support this.
As for the irregular "ᄒ" ending verbs, they might be some short form of N-하다 verbs (similar to the elision of 이 in 이다 after a vowel ending noun?)
e.g. 어떠하다 --> 어떻다 (be) how
Maybe you (or someone, anyone) can help?
• 고양이는 노란색이에요 = the cat is yellow / is yellow in color / is of yellow color
=> 노란 = yellow (adjective)
• 고양이의 색깔은 노랑이에요 = The color of the cat / the cat's color is [a/the] yellow
=> 노랑 = a/the yellow (noun)
The 2 sentences have the same meaning but their grammatical constructions are different.