So the Aithean has been base painted.
The track units and the body were undercoated separately. Inverted, they were sprayed with Citadel Chaos Black. The right way up they were undercoated with Citadel Mechanicus Standard Grey.
The treads were painted with a mixture of Vallejo Black, Vallejo Black Grey and Army Painter Chaotic Red from a wet palette. A redder mix was used for the exhaust.Literally facing off against a Coftyran Chyweethl.