The button cap is 38% translucent white acrylic spray painted black and laser engraved. I used the same white acrylic material inside the 2 rectangular recesses to try and diffuse the LED further before the button cap. The zip file included has a dxf file to create the cap and the 2 lens pieces. 

The PCB is custom made, I just cut it on a cheap CNC machine. The zip also includes Gerber files and a kicad design file, feel free to modify it to suite your needs. The LEDs used are (1) white 1206 SMD Led and (1) green 1206 SMD led. The resistors i chose are 1206 SMD 82Ω. The final component the switch is a 4x4mm SMD Tactile push button