I would like to help anyone in need. I discovered a way to reverse the effect on Artanis' psi blades. The hero model has one blue and one green. The green one belongs to Zeratul, as you already know. However, I looked at the default model, and both blades were blue. I'm sure you also noticed this in the second level of the LotV campaign before it skips to the cutscene? As it just so happens, there is a trigger that can replace Zeratul's psi blade with Artanis' other one.
Trigger: Animation - Clear the "Cover" animation for (Actor of Artanis - Void)
It doesn't look much, I know; but it works. I hope this helps. Maybe it would be useful for modders who want to create stories prior to the events of LotV, or afterwards since Artanis does give the green psi blade to Zeratul's grave after defeating Amon the first time.