Dalek drone

The Dalek drone was the most common Dalek model. (GAME: City of the Daleks) They were used as the main "foot soldier", which led to them very occasionally being called warrior Daleks. (PROSE: War of the Daleks)

Pre-Time War
The original Daleks were created by Davros, who described them as his Mark III Travel Machine. These Mark IIIs had armour cast in gunmetal grey and black. (TV: Genesis of the Daleks)

By the time the First Doctor first encountered the Daleks, they had adopted a silver colour scheme with light blue sensor globes and midsections. These versions lacked slats on their midsection and instead depended on static electricity from the floors of the Dalek City for power. (TV: The Daleks).

The Daleks seen in England during the 22nd century Dalek invasion had a colour scheme identical to their predecessors (save for a silver eyepiece instead of black), but, in order to move on non-metal surfaces, had radio dishes mounted on their backs for external power and larger bases. (TV: The Dalek Invasion of Earth)

The Daleks later adopted vertical slats as a more efficient means of drawing external power from their surroundings. (TV: The Chase onwards)

Later, the Daleks readopted the gunmetal grey colour scheme used by the Mark III Travel Machines, (TV: Day of the Daleks) although the Daleks that were stranded on Exxilon had a silver and black colour scheme. (TV: Death to the Daleks)

The Renegade Daleks adopted a battleship grey and black colour scheme during the Imperial-Renegade War while Davros' Imperial Daleks had a separate, white and gold colour scheme (although these were effectively a different variant of Dalek). Other changes included the ability to hover. (TV: Remembrance of the Daleks)

The Dalek drones were still identified by their grey casings at the beginning of the Second Dalek War of the 26th century (TV: Frontier in Space, Planet of the Daleks) but the casings were altered as the war went on. By the end of the war, Dalek soldiers had a much heavier and more solid look with a distinctive bronze finish, an expanded base, larger cylindrical indicator lights, and a blue-lit eyepiece. (PROSE: Prisoner of the Daleks) However, they reverted back to the simpler grey casings once again after the war was finished. (TV: Destiny of the Daleks, Resurrection of the Daleks, Revelation of the Daleks, Remembrance of the Daleks, PROSE: War of the Daleks)

Time War and aftermath
During the Last Great Time War, the Daleks reintroduced the bronze casings from the Second Dalek War. The basics of the design became standard for all Daleks. (PROSE: Prisoner of the Daleks, I Am a Dalek, Engines of War, TV: The Last Day, The Day of the Doctor, Dalek) This design was much more advanced than the previous model, with a swiveling mid-section that allowed the Dalek a 360-degree field of fire and a force field that fully disintegrated approaching bullets. The design also added a new feature to the eyestalk: if something was obstructing its vision (such as paint), a heat discharge could melt the obstruction. It was also able to regenerate itself by absorbing electrical power and the DNA of a time traveller. The manipulator arm was also able to crush a man's skull in addition to the technology interfacing abilities shown by earlier models. (TV: Dalek, The Stolen Earth) The four unique Daleks who comprised the Cult of Skaro had the built-in "Emergency Temporal Shift" functions. (TV: Doomsday)

New Dalek Empire
The drone casings of the New Dalek Empire were identical to the bronze casings of the Time War Dalek Empire. One minor variation, the Vault Daleks (found aboard their space station the Crucible) possessed a specialized manipulator arm with eight "digits" but were otherwise identical. The mutants inside the all the New Empire casings were grown from the cells of Davros' own body.

New Dalek Paradigm
When the Dalek race was successfully restored using the Progenitor device, the first five individuals of the New Dalek Paradigm emerged. Their casings were larger than their predecessors' and the new drone was bright red, but was otherwise no different from its superiors such as the Strategist Dalek and the Scientist Dalek. (TV: Victory of the Daleks) While the design of the red Paradigm drone was initially mass-produced, (GAME: City of the Daleks, COMIC: The Only Good Dalek, GAME: Return to Earth, GAME: The Eternity Clock) the Daleks ultimately chose to return to using the smaller bronze Time War model as the standard drone, with the larger red version being elevated to a higher position and given a more metallic burgundy colour. (TV: Asylum of the Daleks, The Time of the Doctor, Into the Dalek COMIC: The Dalek Project, PROSE: The Dalek Generation)

Behind the scenes

 * Colin Baker uses the Paradigm Drone Dalek to secure a part in the 50th Anniversary Special in The Five(ish) Doctors Reboot.