Green is definitely sound output (you can connect stereo headphones or 2. 1 stereo).

Black-and-gray audio, hehe, you can use 5. 1 or 7. 1 channel speakers, but you should also set them in the sound card options of the system!

My home has a 5. 1 speaker, which is connected with black and green.

Blue, usually connected to a tape recorder or CD player, can record MP3 with good sound quality (for example, school educational tapes can be recorded in computer format and played on the computer).

That's it. In short, usually you just need to pick up the green one, and if you want to talk, pick up the red one!