Strategist Dalek (New Dalek Paradigm)

The Strategist Dalek was one of the new species of Dalek that emerged from the Progenitor in 1941. The first Strategist Dalek destroyed an "Ironside" Dalek and the leader gold Dalek. It worked most of the machinery inside the Dalek ship and escaped through the time corridor with the Supreme Dalek, Eternal Dalek, Drone Dalek and Scientist Dalek. (DW: Victory of the Daleks)

Personality
The Stratagist seems to be the only one of the other four colored Daleks that speaks, and appears to always stay close to the Supreme. This is proven several times in the episode. First it comes out next to the Supreme. Second it stands next to the Supreme while saying "Sheilds intact.Pulse still Active" Then it appears on the TARDIS screen standing close by the Supreme while the Supreme reveals about Gracewell being a bomb. It could be that the Blue Dalek is a very eager creature, if not loyal.

Behind the scenes
According to Doctor Who Confidential, the name "Strategist Dalek" was coined by Mark Gatiss as one of the new styles of Daleks. Gatiss also coined the names of the White Supreme, Drone and Scientist Daleks.

Matt Smith stated in Confidential that the "blue" Dalek was his personal favourite of the five Progenitor Daleks.