Pro Tech has quite a few colors, some granite looking ones too now so it might be in there. As for finding the color, there are lots of suppliers but I have not found Granite Dust anywhere. Lots of textured ones that look like granite, marble, slate, etc. but not that specific one.

Glitter PP

Textured PP

Any of those come close? Maybe a picture of what you have might help someone to match it with a different name.