Red Dalek

Before the Last Great Time War Red Daleks were a type of Dalek bred for intermediate roles between the less intelligent Blue Daleks and the Daleks that served as their immediate superiors, the Black Daleks. Unlike Blue Daleks, they were capable of independent thought, allowing some measure of independent action. (PROSE: War of the Daleks) Like Black Daleks they were capable of holding the rank of Supreme Controller. (AUDIO: "Death to the Daleks!")

Early history
The earliest known Red Dalek was in charge of the construction of the Sky Seven Space Station when the Mechanoids made their opening volleys in their war with the Daleks. The Red Dalek Leader spared the life of a raving mad Dalek because he correctly believed it was tied to the detected transmissions of alien signals. He located and exposed a camouflaged Mechanoid Interceptor and destroyed it before it could flee. Two more Interceptors arrived, both protected by force fields. He ordered the Daleks to retreat but his Dalek flying saucer was melted as he screamed about the heat and the light. (COMIC: Eve of War)

Following the destruction of Skardal, a Red Dalek was with the Dalek Emperor as he watched the Terrorkons run rampant. The Red Dalek suggested they simply kill off the Terrorkons, but the Emperor told him the Terrorkons were part of the city's defence system and simply had to be constantly outwitted. When a lone Terrorkon stole a missile powerful enough to destroy the city, the Emperor took the Red Dalek with him to stop it. Reaching the caves in the mountains through the pipe systems, they found the missile activated and close to detonation. The Red Dalek defused the missile. (COMIC: The Terrorkon Harvest)

Later History
In the year 4000 when the Daleks made an alliance with the Outer Galaxies and planned to destroy the Solar System with the Time Destructor, the First Doctor interfered and replaced the Time Destructor's Taranium core with a fake one. Upon learning of the Doctor's deception, the Daleks contacted Skaro and the Dalek Prime sent a Red Dalek to Kembel in a Dalek time machine. They pursued the Doctor's TARDIS to ancient Egypt and successfully recovered the core but the Red Dalek did not survive the mission, being destroyed by rocks in a fight between the Egyptians. (PROSE: The Mutation of Time)

The failure of the Time Destructor plan led directly to the Great War which lasted over a millennium. The Emperor tried to win the wars by blackmailing the Second Doctor into discovering the Human Factor and, by extension, the Dalek Factor. A Red Dalek, acting as an emissary for the Supreme Council, oversaw the experiment on Earth in 1866 and returned to Skaro with the other Daleks upon its completion. Other Red Daleks were also present in the Dalek City at the time but the Doctor believed them all destroyed along with the rest of their race when he ignited a civil war against the Emperor's Black Daleks and the rebelling Daleks reconditioned with the Human Factor. (PROSE: The Evil of the Daleks)

Many Red Daleks, among other ranks, were present on Skaro shortly after the Imperial-Renegade Dalek Civil War when the Dalek Prime placed Davros on trial. Like all other ranks with the exception of the Dalek Prime's elite Gold Daleks, the Red Daleks were divided in loyalties - some were loyal to the Dalek Prime while others supported Davros. Davros's supporters were believed to have been wiped out in a brief but devastating battle which erupted when a Black Dalek supporting Davros attempted to assassinate the Dalek Prime. (PROSE: War of the Daleks)

Other red Daleks
Numerous Daleks have been red, unrelated to this caste system. Zeg's casing changed colour during an accident in an engineering lab. (COMIC: Duel of the Daleks) Storm-Blast Daleks were red. (COMIC: City of the Daleks) Some Daleks were also covered with red lead to resist corrosion on planets with humid environments, like Venus. (PROSE: Red for Danger)

Among the Daleks of Azhra Korr, the First-Born, Alpha, had a red casing, although his role and his title were more like that of the Dalek Prime on Skaro. (COMIC: Children of the Revolution)

A race of Daleks newly created from Davros' cells after the Time War were led by the red Supreme Dalek, who also was the highest ranking among his Daleks. The Supreme Dalek was destroyed by Jack Harkness. (TV: The Stolen Earth/Journey's End)

In the New Dalek Paradigm, the red Drone Daleks were initially the lowest ranked. (TV: Victory of the Daleks) Later, standard Dalek soldiers were once again identified by a smaller bronze casing and the red drones were given a higher status. (TV: Asylum of the Daleks)

Behind the Scenes
Both Dr. Who and the Daleks and Daleks' Invasion Earth 2150 A.D., the remakes of The Daleks and The Dalek Invasion of Earth starring Peter Cushing, feature a Red Dalek. In the first film, it is the second-in-command to the Black Dalek, and in the second film it appears to act as the Dalek Saucer Commander while the Black Dalek and Gold Dalek command the the invasion. They were the first ever Red Daleks to be seen on colour film but the show itself would not feature a red Dalek until The Stolen Earth in 2008.