Hi, apologies if this is in the wrong section.

I am looking to cast a polyurethane/polyester piece with a finish similar to this http://www.intertronics.co.uk/products/opt4220.htm.

The finish will be from 2-3mm thick and needs to be able to allow small LED's underneath the sheet to be seen from the other side.

As I am new to the world of casting, I'd like to ask if this finish is possible from just using a small amount of white colour pigment, or if I need to use a different kind of additive to the resin before casting.

Thank you.