Many beginners may have wondered why PCBs are usually green. This is because the solder mask color is usually green. This is to say, the PCB color is the solder mask color. In fact, solder masks can be in any possible color if only the silk screen text/symbols can be easily distinguished from the solder mask.
The solder mask color has no effect on PCB functions or performances. There are no rules about solder mask colors for PCB uses. But there are some views of solder mask colors below.
Green color: green is the most common solder mask color. It is easy to see the silkscreen on green PCBs. And green is comfortable for the eyes.
Black color: some people think PCBs in the black color look advanced. It may be correct, but aesthetics are subjective. PCBs for power supplies often use a black solder mask.
White color: white solder mask reflect much light shedding on the circuit board. PCBs for LEDs often use white solder masks, but we also have manufactured aluminum PCBs with black solder masks for motor front lamps. It should be noted that we often use white solder mask ink with an 85% of light reflective rate to manufacture LED PCBs.
Red color: PCBs with gold fingers, such as graphics cards, often use a red solder mask.
Apart from green, black, white, red, PCB solder masks can also be blue, yellow, mink, purple, pink, brown, and transparent.