Esschem  has produced acrylic polymers and monomers for the manufacture of audio products for many decades
The audacryl and audiflex systems are widely used where hard and flexible acrylics are required for the device casing or soft tips. 
These polymer systems are available in self curing ( RTC ) and heat curing ( HC ) versions, and in a range of colours to match various skin tones.
Colours can be derived from the shading of the polymers, or to achieve transparent shades, using coloured liquids.