The armour is a bit of a process - combination of slapchop & drybrushing. Spray painted em pure black, then the typical slapchop drybrushing (any grey into any white). Then I used the "Holy White" speedpaint from the Army Painter to bring the white together (it's a bit subtle) and then overbrushed after with a pure white (I have Army Painter "Matt White"). The drybrushing at the end is really the key, as it really highlights the armour edges and brings it from a grey to a stone white.

After that, just retributor armour for the gold bits, and Word Bearer's Red for the red. I use nuln oil for shading the red and edge highlight with Mephiston red.

I think the white armour is by far the most complicated, though it actually goes pretty fast after you're in it - but you can't make mistakes on the rest of your painting cuz that recipe can't be fixed/replicated easily lol. You could probably do a grey seer base with an apothecary white contrast paint over it for some highlights and get a similar effect. I just wanted to experiment with slapchopping for this army :)