Yellow is another word for "hello".

Street name for the prescription drug Norco.

IE: "are you Yellow?" A mem used for "Yellow socialism" was also a Marxist term of abuse for all non-Marxist socialists. Pierre Biétry coined the term "Yellow socialism", as a deliberate contrast to Marxist "Red socialism"

The term picked up in France in the turn of the last century with "yellow union." unions were banned and replaced by corporations organized along the fascist model by the Vichy Regime

"Yellow" groups were strongly opposed to Marxism.

"Yellow" in the United States was used in opposition to immigration, because competition from immigrants reduced wages or took jobs from native-born workers, and sometimes even racism including anti-Semitism

Wikipedia has this described in more detail under "Company union" France

A “yellow” is someone who makes you happy. they make your days brighter and worth living.

to be in a good mood
happiness

Is the cat/player color, when you are playing a cat and mouse game on Starcraft the “Cat” is yellow. There was a joke made in this game in witch brown was given the joke that his probe was full of shit because of his color and his slowness and so someone pointed out during the game that the cats must have to go pee. This joke was created after a two hour long game in witch things were assigned to each color.

1. A word that replaces the word "lemon."
2. Used instead of "lemon" to name the fruit.