I recently built myself a macropad inspired by the Palette from the upcoming Splatoon 3 Side Order DLC.
Doing so required making some custom keycaps. The tops of the keycaps were cut from 3mm translucent acrylic and the stems were cut from 3mm clear acrylic, which was then sanded slightly to fit into a kailh choc switch.
I’ve attached the files I used to make the keycaps. Note that they’re designed to be aligned off-center from the middle of the switch; you can see from the PCBs above that the LED is placed immediately below the keycap allowing the colour to illuminate directly through.
You could certainly try designing your own board to use a centered keycap though you may need to consider how to lay out the LEDs for even illumination.
The keycaps DXF file comes with black, red and green lines. The black lines are set as a lower power cut, defocused so that the line comes out wider. The red and green lines are normal cut power/speed.