Does warpstone have to be greenish (lore-wise)?

And let's forget the "your guys" thing for a second. While I do love to do that and love coming up with custom lore and explanations on why things look different than box art - I still want to stay within the borders of the pre-set lore.

And I simply don't know enough about warpstone. Can it just be literally any color and green just became the box art? Or is it always green even as described in lore? Can it change colors with some refining or outer changes? What "excuses" could you think of that would make warpstone for example purple or blue?