Ever noticed that almost every circuit board is green – from TV remotes to smartphones? Turns out, the board itself isn't green at all! It's actually a protective layer called solder mask. In this video, we uncover the fascinating reasons behind the iconic green colour: Cold War military testing, human biology (our eyes are most sensitive to green!), manufacturing cost, and even chemical advantages like faster curing and tighter clearances. Plus, why other colours like black and blue are gaining ground – but green still reigns supreme.