Use environmentally-friendly pigments.
All the PU foam tires can be produced in different colors as your request.
Rim=Plastic rim;Steel Rim;Sprayed metal rim,etc.
Bearing=Plain bearing;Neddle bearing;
Ball Bearing;Precision bearing;etc.
Fixed caster;Swivel caster; Swivel caster with brake.
Produce prodcuts as your design.
With different size,pattern,hardness,etc.