Sorry to burst your bubble, but that is not the case. Ner'zhul = Blue control showing the energy flowing through the helm.
Arthas was never in control. He was lost the moment he found Frostmourne. Why else would Bolvar wear the helmet if he has all the power in the world? The helm represents the power over the Scourge as a commander. It obviously has special powers which neither Bolvar nor Arthas has. The blue eyes and the blue Frostmourne was the visual representation of that.
Remember when we defeat Arthas in ICC? His blue eyes fade away in his final moments when he regains his humanity and sanity from the Lich King and speaks clearly:
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