What's the material and manufacturing process required for achieving this "hidden LEDs '' effect

*Initially posted on the industrial Design forum but think this is more the right place.

I am designing a product and I would like to incorporate some LEDs inside the casing in a similar fashion as in the Ember mug product. Here are 5 seconds of video showing what is the effect I would like to achieve with the hidden LEDs:
Let’s call this the ‘Hidden LEDs method’, because there is no visible acrylic diffuser on the mug like in many products that use backlighting nor is there an apparent overmoulding of clear acrylic allowing a backlight from an LED to shine through.

From the description of the Ember product in their page it says:
“This stainless steel coffee mug with an updated scratch-resistant ceramic coating …”. The guy on the video speaks of this coating as plastic coating.
Now, my product will be molded with a matte black ABS plastic material ideally the same as the cup. However, I can’t find any information on the hidden LEDs effect. Could you help me with the following questions:
-How can they implement this? Do they use any other materials inbetween the LEDs and the ceramic coating?
-Is this ceramic coating they are using transluscent? And is it all across the surface or is it transluscent only in the area around where the LEDs will be shining through.

The casing for the mouse will be ordered with an online quoting service such as protolabs https://www.protolabs.co.uk/ . So I would like to see if they can handle the materials and process described in this thread.
The mouse will be designed by myself in Solidworks so I can design the exact shape I prefer, as long as I know approximately what the manufacturing process will be and type of materials used.