Actually if you look at Trikes sword and Fistos sword, they are the exact same, just different colors.
Though I do agree having rainbows power swords was always lame IMO. I do however agree with He-Man having the grey/silver one and Skeletor having the purple/black one. In my version whoever made the sword of power (He-Man) made it for good, but in turn also made the sword of evil (Skeletor) to balance good and evil.