The Guardians of Celeres primarily wear dark green Power Armour with the exception of the shoulder plates which are white. The Aquila or Imperialis on the chest plate is silver. The black squad specialty symbol -- Tactical, Assault, Devastator, or Veteran -- is located on the right shoulder plate. A white Roman numeral is centred on the squad specialty symbol, indicating squad number. The colour of the shoulder plate trim indicates company number in accordance to the Codex Astartes -- i.e. White (1st Company), Yellow (2nd Company), Red (3rd Company), etc.
The Guardians of Celeres' Chapter badge is a large black skull, centred between a pair of Greek letters -- "Sigma" -- which are addorsed (facing away from one another), on a field of white.
- Adeptus Astartes: Successor Chapters (Limited Release Booklet), pg. 48