Hey all, recently I dug in to a few of the novels that feature the White Consuls, as well as a survey of how they've been depicted over time in all Codex & Manual versions. Here's my comprehensive guide on heraldry that follows canon sources as closely as possible, with attempts to fill in the gaps when official sources are lacking.

Colours

The most recent official material depicting White Consuls shows this colour scheme, which is lighter than earlier depictions and isn't a simple inversion of the Ultramarine Macragge Blue.

• Primary: White Scar
• Secondary: Thousand Sons Blue

Sources:

• Captain Messinius model
• Joytoy White Consul figures

Ultramarines Inversion Rule

Codex: Ultramarines 2nd Ed., Pg 42: "This Chapter's white and blue colour scheme is virtually the exact opposite of the Ultramarines'. For example, Veteran White Consuls have blue helmets and all White Consuls have blue tactical markings."

Heraldry

Battle Brother

• Helmet: White
• Knee: Empty/white
• Sources: Image 1, Image 2, Image 3

Veteran

• Helmet: Blue (Note, the Joytoy Bladeguard Veteran figure has a white helmet, so this may be a permissible variant, but other official sources cite blue)
• Knee: Empty/white
• Sources:
  • Dark Creed, Ch. 7: "Behind this defiant warrior stood a semi-circle of veterans, their helmets regal blue and their spotless white armour swathed in blue tabards."
  • Codex: Ultramarines 2nd Ed., Pg 42: "For example, Veteran White Consuls have blue helmets and all White Consuls have blue tactical markings."

Sergeant

• Helmet: Red with Iron Skull
• Knee: No direct evidence, but extrapolating from Cpt. Messinius and the UM inversion rule, could be white with blue chapter symbol or blue with white chapter symbol.
• Sources:
  • Fateweaver, Ch. 1: "‘Is everything well, brother?’ said the red-helmed sergeant."
  • Fateweaver, Ch. 1: "Beside him Phobos shifted. Freshly attached purity seals hung from his shoulder guards, and he held his crimson helmet in the crook of his arm."

Veteran Sergeant

• Helmet: Blue with white inscribed laurels (unclear on Iron Skull, but probably safe to assume it's present) (Laurels may look like: Example 1, Example 2, Example 3)
• Knee: No direct evidence, but extrapolating from Cpt. Messinius and UM inversion rule, white with blue chapter symbol or blue with white chapter symbol.
• Sources:
  • Dark Creed, Ch. 6: "Their sergeant, whose helmet was royal blue with a white laurel painted around its crown, rose to meet the charging Word Bearers, and Khalaxis threw himself forwards to meet the challenge." (Unclear from the text but given other descriptions of red-helmed Sgts, this is likely describing a Vet Sgt.)
  • Dark Creed, Ch. 10: "A shotgun blast took one of Marduk’s companions in the back, knocking him forwards and into the path of the blue helmeted veteran sergeant of the Assault Marines [...]"

Lieutenant

• Helmet: No direct information, but following UM inversion rule, helmet would be white and stripes would be red in the centre and blue on either side. Another alternative could be one red stripe and no side stripes (leaving them white to blend with base armour colour).
• Knee: No direct evidence, but extrapolating from Cpt. Messinius and UM inversion rule, blue with white chapter symbol.

Captain

• Helmet: White (Cpt. Messinius lacks an Iron Skull but could be a quirk of his personal heraldry, and likely safe to assume it's standard for most Captains.)
• Knee: Blue with white chapter symbol
• Sources:
  • Captain Messinius model
  • Captain Messinius Joytoy figure
  • Dark Creed, Ch. 7: "There in the doorway stood the figure of a White Consul. A tall white crest rose above his gold-edged helmet." (Description of 2nd Company Captain Augustus)

Champion

• Helmet: Blue
• Sources:
  • Dark Creed, Ch. 10: "A warrior armed with power sword and buckler, his blue crusade-era helmet adorned with a red crest of stiffened hair, stepped in front of the Chapter Master, his voice ringing with challenge."

Librarian

• Armour: Blue (presumably the darker Kantor blue like standard Codex librarians)
• Sources:
  • Fateweaver, Ch.1: "Cyrus sat alone and watched the holo-recording. He wore no armour; his suit of blue Terminator plate was being cleansed and re-blessed after his journey to the surface of Kataris."