Most of today’s printed circuit boards are green because they are made from a glass-epoxy which is naturally green, or they are coated with a solder mask which is usually green too! The role of solder mask is to insulate and protect the underlying copper traces from oxidation and humidity, and to prevent eventual short circuits during wave soldering. Although green is used as industry standard color for solder mask from many manufacturers we can say almost any colour could be used, depends on the client's specifications. Another reason to choose green over order colours is that green is less irritating to the eyes, the workers and engineers need to stare at the PCB for a long time in production or maintenance. Green is friendly to the eyes and not easy to suffer from eye fatigue.