Colours.

[zabado]

When did colours start to mean the way we feel ,?
Green. Envy.
Blue. Sad.
Yellow .Cowardice
Red. Rage.

[Quizmonster]

Blue, meaning sad, is first recorded in the 1830s in the phrase "it's a blue look-out". This was reinforced about a century later by jazz musicians referring to a "blue note", one which was off-pitch, suggesting a melancholy atmosphere.

[Quizmonster]

Further to my earlier answer...
Yellow was originally associated with jealousy from the 1600s, but did not become linked to cowardice until the middle of the 19th century in America.
Red was at first linked with shame from the 1200s, but - also about the middle of the 19th century - it took on a connection with anger, presumably because of the colour of one's face when discovered in something shameful or anger-provoking.
Green was originally linked with fear in the 1500s, but Shakespeare was first to refer to ‘the green-eyed monster', meaning jealousy, a century later.

[zabado]

Interesting that William Shakespeare got a mention.
Thanks Quizmonster.