Note: green apples are also commonly called 청사과. And yes, 청 is yet another name for green AND blue (청와대 - Blue House)
I'm not exactly sure 청사과 is common, but either way it is non-standard.
When you eat green apple
Is the 색 always needed? I see for example bluebird was 파란새, I think
파란 is a conjugated form of 파랗다. 녹색 always requires 색, but 초록 can stand on its own.
What happened to 조롱색 ???