Shakespeare mentions these in Antony & Cleopatra (Act 1, Scene 5)
“𝔐𝔶 𝔰𝔞𝔩𝔞𝔡 𝔡𝔞𝔶𝔰, 𝔴𝔥𝔢𝔫 ℑ 𝔴𝔞𝔰 𝔤𝔯𝔢𝔢𝔫 𝔦𝔫 𝔧𝔲𝔡𝔤𝔢𝔪𝔢𝔫𝔱”.
The reference is to the years of inexperienced youth – green is the fresh colour of young vegetables used in salads, and represents anyone who is young and lacking in experience. This also accounts for the use of the terms ‘green’ and ‘greenhorn’ for anyone considered to be a novice, raw hand, or simpleton.
P.S: and salad is delicious with the right dressing of course.