From ThreeA Wiki
The Sand Devil Corp  is a desert unit in WWR and WWRp that sports a unique colorway that appears desaturated with stronger attention to the brown hues (as compared to Desert Combat). The decals in this colorway include a skull and the 666th logo.
WWR Sand Devil Robots
A list of WWR Robots that are a part of the 666th colorway:
WWRp Sand Devil Robots
A list of WWRp Robots that are a part of the 666th colorway: