One common production method for lightpipes is the overmold . This method uses an inexpensive light diffused plastic overmolded with a black case to generate a light-pipe.
The “Win” keyboard key is one good example.
The black key body has a hole; during manufacturing, this hole is filled with a white diffuse plastic in a process called overmolding.
We then flashed the key underside with a phone flash and you can see the glowing windows logo.