While we cannot make actual plastic enclosures out of High Density Polytheylene (HDPE), we can CNC mill it from various sheet sizes to offer flat plastic parts - prototype and production. Typically, sheet sizes come in 4x8's and in thicknesses from ..125 to 1" thick.
The most common HDPE options have a "natural" white/beige color to them, but some trade names offer some color variation (mainly white and black) and textures. These would include:
Due to it's resistance to solvents and other fluids, HDPE can be good for industrial environments, outdoor applications, and other hearty funcationality requirements. These could include: