Thank you!
I mostly use Citadel paints - the armour is a Grey Knights Steel base, washed with Nuln Oil. It then has a layer/bad attempt at TMM with Stormhost Silver and finally a (careful) watered down wash with Drakenhof Nightshade.
Took a few goes to get the blue wash right - settled for pure wash in the recesses, and a very watered down one (pretty much a glaze I guess) over everything else.