An Overview Of Republic/Imperial Uniform Colors

In the Republic and its successor states individuals in service of its military and civilian organizations commonly wore a universal service uniform.  Though the uniform differed slightly between organizations and time periods, a basic standard existed amongst the uniforms of most members of the Republican/Imperial apparatus.

One key difference in uniforms used to identify members of a certain branch was color.  Specific branches of the Republic/Empire had colors used to identify their uniforms.  To avoid wasting time I'll get into the data.

PT 1:  The Galactic Republic.
The Galactic Republic used many different service uniforms throughout its long history.  As early as the Naboo Blockade the Republic had adopted a new system that would be used by its personnel until its transformation into the Empire.

Judicial Department - The Judiciary was the central military and law enforcement department of the Republic until the Clone Wars necessitated a proper military.  The Department included the Judicial Forces and the Security Forces; members of both were known to wear dark blue service uniforms.[1][2][3]
Senate Guard - The Senate Guard were the elite police force in charge of protecting the Galactic Senate.  While part of the Judicial Department, their suits bore different colors.  The tunic sported a noticeably lighter shade of blue alongside black pants.[4]
Republic Navy - Officers in the reorganized Republic Navy wore a variety of uniform colors.  Admirals and Captains were almost exclusively seen wearing olive-drab uniforms.[5][6][7]  Lower ranking officers usually wore a greyish-blue or white suit.[5]
Republic Army - I can't think of any outright visual appearances of the Clone Wars-era Republic Army.  It is known the Army was founded from PSFs and the Judicial Forces.  My best guess is the uniforms of the Judicials would carry on to the new department (PSFs had no standard garb).
Grand Army of the Republic - Officers were seen wearing blue-grey while others wore a darker grey uniform.[5]
Medical Specialists - Officers serving medical roles were seen to consistently wear white uniforms, sometimes with brown belts, gloves and boots.  During the early Clone Wars, medics wore badges on their shoulders.  Towards the end of the war the officer's badges were moved to their chest, left of their rank badge.  The new uniforms also sported hats with red stripes on the shoulders and cap.[5]
Republic Service Organization - Members wore tan jackets with a black skirt.  Their caps could either be black or tan.[35][36]
Potential Judicials - A captain appeared on a ship resembling a Judicial vessel.  The ship's captain wore a red uniform.  An officer under his command wore either a greyish or green uniform (The lighting made the color a bit ambiguous).  Could these be examples of Judicial ranks having different colors?[8]
Republic "Generals" - The ORSF was a particularly large paramilitary organization run by Republic Senator Ranulph Tarkin.  The Security Force was intended to be the official Republic Military, though it was never more than a mere PSF.  Tarkin himself held the rank of General within the ORSF, wearing a red tunic with blue pants.  Could this have been an official uniform for Generals?[9]
Republic Moffs - Wilhuff Tarkin was a Sector Moff as well as an Admiral.  He wore an olive-drab uniform standard amongst Admirals.  Was this representative of the Moff uniform?[5]

PT 2:  The Galactic Empire.
Having been born from the Republic, the Empire inherited its predecessor's equipment.  It took little time for the Imperials to phase out old uniform styles.  The new suit had been seen in the Republic's ranks before, but it now bore the status of standard-issue.

Imperial Slavers - Any information on the placement of slavers in the military structure or their rank and organization is certainly beyond me.  However, one slaver made a clear appearance supervising labor on Weapons Factory Alpha.  This individual wore a rarely-seen brown uniform.[10]
Imperial Security Bureau - ISB agents' outfit consisted of black pants and a hat with a white tunic.[11]  There were exceptions of course; some Agents have been seen wearing grey.[12]  One other case is Commander Alecia Beck, who wore all-white.[13]
Imperial Army - Now there were surely many obscure colors seen in the Army, but the standard was clearly olive-drab.[14]
Imperial Navy - Throughout the Navy officers typically wore olive-drab.  Naval Troopers wore all-black on the other hand.[11]
Stormtrooper Corps - The typical Stormtrooper wore an all-black uniform, not unlike the lesser-skilled Naval Troopers.[11]
Starfighter Corps - Imperial Pilots were seen wearing either olive-drab or black uniforms.[15][16]  Some even wore light-green suits.[17]
Imperial Medics - Army Medics wore a white tunic with blue stripes and a pair of black pants.[16]  Another Medic, who I assume to be the Naval analogue, wore a more regular grey suit.[18]
Imperial Surgeons - Unlike the similar Medics, Surgeons wore an all-teal uniform.[19]
Imperial Diplomatic Corps - Diplomats wore the standard olive-drab suits.[20]
181st Imperial Fighter Wing - Initially the 181st were a standard starfighter wing, wearing olive-colored garb.  After being promoted to "elite" status they gained red stripes on the sides of their uniforms.[15]
Imperial Liaisons - Liaisons provided a bridge between the Imperial government and local forces.  They were seen wearing green uniforms.[21]
Imperial Intelligence Directors - Armand Isard and later his daughter, Ysanne, both wore all-red uniforms.[22][23]
Imperial Intelligence - Similar to the ISB, most Intel agents wore white jackets and black pants.[24]  Also, it wasn't unheard of for agents to wear all-grey.[12][25]
Imperial Inquisitors - Though Inquisitor uniforms soon devolved into a hodge-podge of contradiction, the initial kit was quite standardized; these early Inquisitors were seen wearing grey.[26]
Grand Admirals - Grand Admirals wore one of the most iconic uniforms in the Empire.  The suit consisted of a white tunic and pants along with gold epaulets.[27]
Moffs and Grand Moffs - Trachta, an early Moff, wore a grey suit.[28]  In later years Moffs would be seen almost exclusively in olive-drab.[11]  Rufaan Tigellinus was a Grand Moff as well as a Grand Admiral; he wore a Grand Admiral's uniform instead of the Moff's equivalent.[29]
Ozzik Sturn - Kashyyyk's Captain Ozzik Sturn inexplicably wore an all-white uniform (Military captains almost exclusively wore olive.).[16]  It is unclear what warranted his irregular attire.

PT 3:  The New Empire.
Under the new Empire the uniforms were of a quite similar style to the previous renditions; the main difference being most commissioned officers would wear collars and cuffs alongside the traditional garb.  Color-based identification would certainly persist in this era.

Imperial Mission - Konrad Rus, the head of the Mission, wore a white uniform under his Missionary robes.  In addition he possessed a white collar with gold badges.[30]
Imperial Diplomatic Corps - The only diplomat seen in the new Empire was Director Fehlaaur.  He wore the standard olive-colored uniform.[31]
Imperial Intelligence - Director Calixte possessed a blue-grey uniform.[30]  Imperial Knight Sigel Dare wore an olive-drab uniform while posing as an officer.  She wasn't an actual Intel operative and her uniform was a disguise; the legitimacy of the uniform is debatable.[32]
Imperial Navy - From the bottom to the top it seems most conventional officers in the Navy wore the standard olive-colored uniforms.[33]
Imperial Army - Like the Navy, olive seemed to be the standard color for the Army.[33]  One notable exception: in some scenes it appeared the Army's head, Geist, wore a grey uniform.[34]  At other times he possesses the normal olive suit.[31]
Starfighter Corps - Pilot Gunn Yage wore an all-black uniform.[31]

Military Supreme Commander - Supreme Commander Morlish Veed sometimes appeared in a greenish-khaki uniform.[34]  On other occasions he wore an olive-colored alternative.[30]

Sources:
1. Star Wars: Episode I The Phantom Menace
2. Star Wars: Episode II Attack of the Clones
3. Star Wars 28: The Hunt for Aurra Sing, Part 1
4. Clone Wars Chapter 24
5. Star Wars: The Clone Wars
6. Star Wars: Republic: Dreadnoughts of Rendili
7. Star Wars: Republic: Siege of Saleucami
8. Star Wars 23: Infinity's End, Part 1
9. Star Wars: Republic: The Stark Hyperspace War
10. Star Wars 1: Skywalker Strikes
11. Star Wars: Episode IV A New Hope
12. Star Wars Galaxies: An Empire Divided
13. Smuggler's Run
14. Star Wars: Episode V The Empire Strikes Back
15. X-Wing Rogue Squadron 25: The Making of Baron Fel
16. Star Wars: The Force Unleashed
17. X-Wing Rogue Squadron: The Rebel Opposition
18. Empire 9: Darklighter, Part 2
19. Star Wars: Empire: To the Last Man
20. Star Wars 49: The Last Jedi (Lol)
21. X-Wing Rogue Squadron 26: Family Ties, Part 1
22. Darth Vader and the Cry of Shadows 3
23. X-Wing Rogue Squadron: In the Empire's Service
24. Star Wars: Agent of the Empire
25. Mara Jade: By the Emperor's Hand
26. Evasive Action
27. Heir to the Empire
28. Star Wars: Darth Vader and the Ghost Prison
29. Who's Who: Imperial Grand Admirals
30. Star Wars: Legacy: Broken
31. Legacy 15: Claws of the Dragon, Part 2
32. Legacy 42: Divided Loyalties
33. Star Wars: Legacy
34. Legacy 43: Monster, Part 1
35. The Clone Wars: Prelude
36. The Clone Wars: The Valsedian Operation