why maximum circuit boards like mother boards and all that have a coating of green color ?

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.
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.
Thanks & Regards
Aarti Gupta
askiitians Faculty