Excelsior

Is there a way to dye non-standard hues besides a universal dye tub?
And I mean dying anything.

only thing i can think of aside from the universal dye tub to get sorta "non standard colors" would be greater pigments of tokuno but even that is pretty tame, although there are some nice colors

there are special dye tubs scattered through out the world. also, there are other vet reward special dye tubs.

good luck.

Plus, for one colour and if you're wealthy you can actually purchase it as your guild colour, buy the dyetubs for all item kinds and dye to your heart's content. But that's a very expensive option, to say the least.