Imperials really like black. I mean, everything is a shade of black on black… Vallejo black grey has a gloss that works well for the boots, then the clothes are a Vallejo dark sea blue, with some Citadel lahmian medium for glossy gloves and the helmet. I wouldn’t recommend the black grey on the helmet since you’ll lose the details. I did the dark sea blue, with lahmin medium for gloss, then hit it with Citadel nuln oil to bring out the textures.