Perhaps this would be a good place for Microchip's Charge Time Measurement UnitCTMU PDF
and its ability to easily use capacitive touch buttons. I got to play with
the CapTouch technology on a recent job, and it works wonderfully, including through
1/8" thick Lexan or glass.
A good discussion of the concepts is HERE.
Circuit board could have a RGB LED mounted through a hole from the back side of
the PCB, a protective transparent or translucent poly panel could have the "buttons"
painted onto it, etc. ...
On the fancy side, the pads for the "buttons" could be formed on glass using Indium
Tin Oxide, a transparent conductor.