BLU

From TF2 Wiki

The Builders League United Inc. is a company supposedly specialising in construction, bread production, hydroelectric power and silage. In reality, BLU is merely the front for a major intelligence agency. Beneath the convincing exterior can be found computer racks, war rooms, satellites, rockets and missile installations.

Shortly after the front company was established, agents at BLU discovered that a competing company, Reliable Excavation Demolition, was likewise a front for a rival intelligence agency. The two companies began to take hostile action against one another under the cover of territorial disputes and corporate espionage. Specialist teams from either side are constantly employed to steal vital intelligence from one another, as well as capturing key control points.

BLU favours a more industrial style of architecture than RED, and while its dress code is rather liberal in terms of clothing, it is required that employees dress in blue for easy identification.