This guy is a 1990 sculpt, and appears in the 1991 catalogue as Mark V Heresy Armour 070270/7. The minis on his catalogue page are marked as “Designed by Jes Goodwin and the Citadel Design Team”, and I very much suspect that it’s a Jes Goodwin sculpt but I can’t find a singular credit for it in any catalogue.
Colours used:
Undercoat: Vallejo Mecha Black
Blue: Scale75 Art Cobalt Blue, with some Prussian Blue as a shade, and some Cobalt Blue + Art Black as a shade. Highlighted with Cobalt Blue + Pro Acryl Titanium White
Red: Pro Acryl Bold Pyrrole Red, shaded with Targor Rageshade, highlighted with Bold Pyrrole Red + Golden Yellow
Lenses: Scale75 Art Spring Green, highlighted with Golden Yellow and a touch of Titanium White, shaded with Art Black
Freehand decals are Cobalt Blue + Titanium White
Gold: Scale75 Necro Gold, washed with Targor Rageshade, then Dwarven Gold, then Citrine Alchemy
Base rim: Vallejo Model Colour Black Grey
Base: Soilworks Dark Mud around the rim, then Natural Soil on the inside, then Sand inside that, then Gypsum to highlight the rocks. Natural Soil on the legs.
Silver: Black Metal, shaded with Targor Rageshade, Thrash Metal, Speed Metal
Gold shells: Dwarven Gold, shaded with Targor Rageshade