Yellow

Yellow was a colour of various shades. Egg yolk was a particular kind of "brilliant yolky yellow". (PROSE: Verdigris)

The Sixth Doctor typically wore trousers with yellow stripes. (AUDIO: Piece of Mind)

Mickey Smith drove a yellow Volkswagen Beetle in 2005, but had replaced it with a Mini by 2006. (TV: Rose, The Parting of the Ways)

Two robots, a yellow one and a red one, were sent to Earth to find the heir to the throne of a planet. (TV: The Empty Planet)

The eyes of those exposed to zytron energy turned yellow. (PROSE: Ghosts of India)

Yellow in nature
Eternal Daleks had a yellow casing. (TV: Victory of the Daleks)

The Doradans were a species which possessed yellow skin, (PROSE: The Dream Masters) while the Arunde possessed yellow fur. (AUDIO: The Fifth Traveller)

Culture
The term "yellow" had two connotations on Earth: as a sign of cowardice, and as a racial slur against Asians. While convincing an Asian friend to help her break in somewhere, Ace told him "don't be so yellow," before realizing and regretting the expression. (PROSE: The Hollow Men)

In comparison to other colours like red or black, yellow and purple were inferior psychological triggers in humans. As such, a Yellow Eye of Eternity never appeared in Through the Eye of Eternity. (PROSE: The Book of the War)

The Yellow Kangs had yellow hair and clothing. (TV: Paradise Towers)

Demons Run was placed on yellow alert as the Eleventh Doctor assembled an army from across time and space to rescue his companion Amy Pond and her baby daughter. This period of yellow alert lasted three weeks which climaxed with the Battle of Demons Run. (TV: A Good Man Goes to War)

The Fragile Yellow Arc was one of two epochs in the lives of the residents of the planet Fragrance. It was the time from which a person fell in love until the time they died. (AUDIO: The Fragile Yellow Arc of Fragrance)

Other Information

 * The Eternal Dalek's yellow and black colour scheme was described in The Brilliant Book 2011 as the most dangerous colours found in nature.