All credit goes to to Mediocre Hobbies

Vehicles

Base/Prime Chaos Black
Heavy Drybrush Rhinox Hide
Medium Drybrush Ryza Rust
Medium Drybrush Fire Dragon Bright
Drybrush edges with Leadbelcher
Rough & patchy Mephiston Red in the middle of the panels, leaving edges rusted
Little stippling Evil Sunz Scarlet in red areas

Ork symbols in Celestra Grey

Final light drybrush with Leadbelcher

Ork Krew

Skin Straken Green , Ogryn Camo , Krieg Khaki

Top in Mephiston Red , then scratchy Evil Sunz Scarlet Wild Rider Red and spot Tau Light Ochre
Trousers in Mechanicus Standard Grey then Seraphim Sepia wash
Boots, belts, leather in Black Templar then Seraphim Sepia wash

Base

Rhinox Hide , then drybrush Ryza Rust and Ushabti Bone (be sure to hit the wheels/tracks/tyres too)
Light Rust pigment on base and wheels/tracks/tyres