Yellow was a colour.
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)
The Yellow Kangs had yellow hair and clothing. (TV: Paradise Towers)
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)
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 Demon's Run. (TV: A Good Man Goes to War)
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)
Eternal Daleks had a yellow casing. (TV: Victory of the Daleks)
The Doradans were a species which possessed yellow skin. (PROSE: The Dream Masters)