Paint mask

Spraying is the quickest way to paint a complicated part evenly without obscuring detail, so it is the method of choice in the mass production of toys. To keep the paint spray from going where it is not wanted, a paint mask is made. This is a thin metal shell which conforms to the shape of the painted part. Holes are cut in the mask to reveal the areas of the part which are to receive paint. A separate mask is usually needed for each color used, and many multiples of each are needed to paint many objects at one time, but the term "paint mask" is usually used by Transformers fans to refer to the entire set of masks for one particular figure.

Cheap, lazy redecos
Once a set of paint masks has been produced, different colors may be easily sprayed through the same mask - it's only a matter of changing the paint used. Changing the shape, number, or location of the paint applications used, however, requires a new set of masks, as well as new paint. The extra costs involved in this make such redecoes less common; generally, the same paint masks will be reused.