Computer motherboards and most other electronic circuit boards are generally green in color. This is because such electronic boards are coated with a polymer called solder mask, which insulates and protects the printed copper traces of a motherboard during the soldering process.
Solder Mask Properties
A solder mask coating helps insulate and protect sections of a motherboard where no soldering is required during mass assembly. Solder mask is also necessary for silkscreen printing on a circuit board.
Green solder mask has been a traditional industry standard for decades. Though no specific reason is given for choosing green over other colors, green does have its advantages. Silkscreen printing is easily legible on a green background, for example, and the widespread adoption of green as a standard color enables manufacturers to use other colors of solder mask for prototypes.
With the growing popularity of clear computer cases and case windows, the inner workings of computers are no longer hidden from view. This has prompted some manufactures to experiment with other colors of solder mask, such as red, blue and yellow, to give their products a unique appearance.