User blog comment:ChishioKunrin/Dust: Fire! Water! Lightning! Energy?/@comment-2135507-20140822065804/@comment-4010415-20140822135503

Brown with a yellow shrine. Though, dark yellow can sometimes look closer to brown if you make it really really dark.

Though, we haven't seen any brown Dust crystals. Surely the main four can be mined in their crystal form. We have, however, seen red, blue, yellow, and green Dust crystals.