Green cheese
Green cheese is a term for a fresh cheese, one that has not thoroughly dried yet, nor been aged, which is white in colour and usually round in shape. The Oxford English Dictionary gives a reference from the year 1542 of the four sorts of cheese. The first sort is green cheese, which is not green by reason of colour but for its newness, for the whey is not half pressed out of it yet. The phrase is not commonly used to describe the colour of a cheese, though there are some cheeses with a greenish tint, usually from mold or added herbs. The word "green" for new has other uses, such as greenhorn for an inexperienced person.
In popular culture
The phrase the Moon is made of green cheese refers to the similarity in appearance of a typical round, green cheese and the full Moon. It is commonly misinterpreted to mean that the Moon is green in colour, which does not occur.
John Maynard Keynes made a reference comparing a green cheese to the moon in his 1936 book The General Theory of Employment, Interest and Money. The exact meaning of the sentence is debated, but the equating of the moon with a green cheese is clear.: