Imperial Intelligence exists in rivalry with the ISB. It is a more secretive organisation which concentrates on incisive analysis and more subtle espionage methods. Although the Empire employs vastly more ISB personnel, the superior professionalism of Imperial Intelligence allows it to provide a more potent service. (For instance, no Imperial Intelligence encrypted document has ever been successfully decoded by the frustrated ISB counterparts.)
Imperial Intelligence is more formally an authority of the Imperial Government than the ISB, which was founded from the COMPNOR political party. However unlike the ISB, the command structure of Imperial Intelligence does not appear to involve formal military ranks. Operatives of Imperial Intelligence do not have special titles, and are addressed along the lines of "Agent Loor".
Before the Death of Emperor Palpatine and the gradual decline of the Galactic Empire, the central coordinating authority of Imperial Intelligence was mysterious and invisible to the public and regular military alike. This group, whose membership was strictly secret, was ominously known as The Ubiqtorate.
For a brief time between the Battle of Endor and the loss of Coruscant to the New Republic, a woman named Ysanne Isard displaced the feuding military leaders and the Advisors of the Imperial Court in order to take power for herself. She revealled herself to be Director of Imperial Intelligence. Presumably she was the victor of an internal coup within the Ubiqtorate. The survival of other Ubiqtorate members at that time is unknown, although the Ubiqtorate had resumed operations for the diminished Empire led by Grand Admiral Thrawn several years later.
Imperial Intelligence operatives who are directly engaged in epsionage would not wear any particular uniform. Spies are not supposed to be readily identifiable.
However some Imperial Intelligence personnel are required to liase with military, government and law-enforcement agencies throughout the Empire. Individuals in this role would wear an official or semi-official uniform. Agent Kirtan Loor in X-Wing: Rogue Squadron operated in this capacity. On p.30 and p.33 of that book he is described as wearing black boots and tunic, and reference to the visible hair on his head suggests that he does not wear a cap. It is uncertain whether this uniform is unique to Imperial Intelligence, or whether it might be due to Loor's position as a liason with elements of the Imperial Navy.
Ysanne Isard wore a red military-style uniform. It is unknown whether this is a legitimate and formal uniform for a member of the Ubiqtorate, or whether she invented and adopted this costume when she siezed power in the Imperial Palace.
The present knowledge about the uniforms of the Ubiqtorate and Imperial Intelligence liason officers is summarised in the Imperial Intelligence subsection of Summary of Uniforms.