Really? How did you figure out Sweat of Brow was lightning based? It doesn't make much sense.
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http://ffxiv.zam.com/en/ability.html?ffxivability=29719
Purple icon. Easy.
Look at all the gathering icons, they all correspond to the colour of the crystal they are modified by.
I have yet to see Perfection not work for "Finished Items" both in activating and actually creating successes. I tested this on a variety of different crafts with both stable and unstable orb conditions, even with bold synths on unstables(still worked). As for why it isn't working for some people perhaps they are producing parts or materials, in which case it doesn't surprise me an either or type ability would not work.