CNC panels are made from 5mm white opaque Perspex. Then sprayed grey. Once dry, I use the CNC machine with an engraving tip to remove the paint and etch into the Perspex. This way the panel can be backlit and lights up when dark. Others use a laser engraver to create the text.
Another really cheap way to produce professional back lit panels is with a vinyl cutter available from amazon for around $150. Simply feed the vinyl into the printer and it will cut all the text out and shapes as required.
https://www.amazon.co.uk/Silhouettes-Portrait-Digital-Cutting-White/dp/B076B5PRCG/ref=sr_1_5?ie=UTF8&qid=1536665737&sr=8-5&keywords=vinyl+cutter
Just a quick tip on this one, if you use a laser to engrave your panels buy some light tack application paper from a sign supplier (I use medium tack 305mm rolls) to stick to the top of the painted surface as it helps with any smoke damage caused by the laser process. Just run an old card across the surface to remove any left over paper. Makes a nice crisp no smoke damage sheet.