It's a combination of pigments. First the rub on Sand color from Tamiya. Then a mix of AK's Burnt Rust Red and Ochre Rust. I blend it together with a small fan brush.
It’s just mismatched armor types as the civil war raged on and took its toll on wargear, materiel, force organization. Late Heresy is a fun excuse to kitbash.
That very bright grey? That’s Administratum Grey used as chipping and irregular edges. The black surfaces go from AK Black to a mix of AK Black and Vallejo Dark Grey, layered with an airbrush.
