The base price of any part includes (1) colors. Extra colors require extra set-up and materials.
The engraving process creates shallow pockets in the skin of the part being engraved. Those pockets are then filled with a high grade paint that holds up to the heat generated by the engine.
When designs have colors adjacent to one another, there will be a thin strip of material left between the pocket to serve as a dam, isolating the pockets.