Paint operation
From Transformers Wiki
Transformers toys are often partly or wholly painted. Die-cast metal must always be painted if a tarnished gray finish is not wanted; plastic parts, commonly molded in color, can also be painted to highlight detail or add visual interest.
These painted areas, or paint operations (also commonly called paint applications), on mass-produced Transformers toys, are applied by spraying through a paint mask, in cases where total paint coverage is not wanted. This mask 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 singular term "paint mask" is usually used by Transformers fans to refer to the many actual pieces of metal used to produce one particular figure.
Redeco potential
Once a paint mask has been produced, different colors can be easily sprayed through the same mask — it's only a matter of changing the color of the paint. The extra costs involved in this are negligible, amounting to paying the deco artist to pick colors. Changing the shape, number, or location of the paint operations, however, requires a new set of masks.
Paint limits
There are limitations to what can be painted on a toy. Some plastics used in the toys' construction cannot hold paint properly, so they must remain wholly the color they were cast, unless a sticker is used.
Also, the number of paint operations is often given a maximum "do not exceed" number to keep costs within a certain range. This number is usually predetermined on the basis of size class. For instance, every Deluxe sized figure of a given line will have the same number of paint operations as all the other Deluxe figures. And it may take more paint operations to cover a part than at first thought: simply painting the outer surface of a cylinder may take two to four paint operations, and then another for the ends, if desired.
Another limiting factor is the kind of paints used. While basic colors are generally inexpensive and may only require one layer of paint to show properly, metallic and especially "metal flake" shades can require multiple coats so that they don't appear discolored or translucent. In general, manufacturers consider each layer to be a separate paint operation, meaning one detail can count as anywhere from 2 to 5 operations from a budget perspective. In such cases, it can actually be cheaper to cast a part in metallic plastic and then paint all but the detailing in the base color.
Since Hasbro and Takara use multiple factories for having their toys manufactured, the way of counting paint operations can differ between factories: For example, do two eyes painted the same color count as one or two paint operations? In the past, this could have both bad (the factory counted more paint operations than Hasbro, thus Hasbro had to drop one or more of them) and good results (the factory counted fewer paint operations than Hasbro, allowing Hasbro to add another).
