Yellow has always been associated with treachery, cowardice, jealousy, and inconsistency. The medieval star of yellow color branded the Jews as having betrayed Jesus, the medieval yellow star was even continued by the Nazis. Also, Judas Iscariot (one of the most well-known traitors) is usually portrayed in medieval times wearing yellow garments.
In France, the doors of traitor’s houses are painted with bright yellow. Meanwhile, in Spain, Inquisition victims were forced to wear yellow as a symbol of treason and heresy. In America during the 1800’s, there was a popular expression “yellow-dog” to describe anything that was worthless. Even today, the color yellow is strongly associated with negative things.
For example, there is an expression “yellow-bellied coward” that persists in modern times. The combination of connotations associated with yellow (cowardice, treason) and the guts (heroism, stamina, grit) is apparent. A person with guts is known to have courage which leads to heroism. By associating yellow with the gut, the term “yellow-bellied coward” became a way of saying that a person lacks courage.
But why the seemingly strong dislike for the color yellow? Well, there are actually many theories. For example, in the 1890’s, Asians were seen as a “threat” and yellow was used to imply deceit. However, it is highly unlikely that the origin of using yellow to imply negative characteristics have racist undertones. The more likely source is the medieval medical belief that there are four humors (bodily fluids) within the human body.
The fluids are said to determine the mental and physical condition of a patient. If they are out of balance, they either got physically sick or mentally ill. The four fluids consisted of blood, black bile, the yellow bile, and the phlegm. The yellow bile can make you irascible, choleric, and sick. In addition, cholera (one of the most feared disease at the time) has a symptom wherein the person has yellowish diarrhea. It is easy to make the connection between yellow and inconsistency since then.
Other uses of the yellow color include using it as the symbol of quarantine. Victims of the yellow fever were isolated as not to contaminate the rest of the population. Also, there was a time of “yellow journalism” in 1895 wherein newspapers used sensationalism to attract readers. It is ironic the yellow, the color that is literally associated with everything cheerful (the sun, nature, flowers, etc) has become so negative especially if it is used metaphorically.
P/S: Especially dedicated to the coward (you-know-who) who was afraid for confrontation...Boohooo....!