Why on Earth should the Star Wars prequels have been in black and white, you ask? Well, here's a few reasons...
1. The visuals/tech would have better blended with the OT. Even the most restrained modern filmmaker would have had a hard time not making the tech in the PT look more advanced than that of the OT. And GL is hardly that most restrained filmmaker. But the primitive aura of b&w could have helped keep the OT and its seventies haircuts looking fresh.
2. The ANH beginning would remain spectacular. A b&w trilogy would also preserve the "wow" moment of ANH's first shot. In-universe linear viewing would have shown ships and space battles up to that point, but never in color.
3. It could allow for more violence. GL obviously invented those hideously lame battle droids to avoid having the noble Jedi carving up living beings right and left. But if it'd all been b&w, that wouldn't have been nearly as gory or shocking. See: the b&w portion of the dojo fight in Kill Bill 1.
4. It would have been educational. Too many younguns these days turn their noses up at b&w. Heck, even I did back in the day. This would have compelled them to see and enjoy b&w films from an early age.
5. It could have encouraged more focus on story, dialogue, etc. How many hundreds of hours were spent on choosing the various colors of the trilogy? Hours that could have been used coming up with decent scripts. Less color-filled eye candy to show off could have forced GL to craft the best possible film, not special-effects showcase.
6. It would have been better suited to the dark tale generally. B&w film can have a nightmarish quality to it (Psycho, The White Ribbon, the dvd version of The Mist). Anakin's tragic fall to evil would have been well served by the format.
Sure, there would have been downsides. The art direction, (along with John Williams' work) is the only truly exceptional aspect of the trilogy, and much of its flavor (and thus merchandising potential) would have been lost in grayscale. (Padme's rainbow dress...
) And while the PT we got hardly fits in visually with the OT, it would still have been odd for the universe to suddenly develop color halfway through. Finally, so long as we're dreaming, we could just say the PT should have had better stories, scripts, etc. and leave it at that.
Still, for the above reasons, I think a well-done PT might have been truly awesome. It would certainly have been a bold and thought-provoking move...
1. The visuals/tech would have better blended with the OT. Even the most restrained modern filmmaker would have had a hard time not making the tech in the PT look more advanced than that of the OT. And GL is hardly that most restrained filmmaker. But the primitive aura of b&w could have helped keep the OT and its seventies haircuts looking fresh.
2. The ANH beginning would remain spectacular. A b&w trilogy would also preserve the "wow" moment of ANH's first shot. In-universe linear viewing would have shown ships and space battles up to that point, but never in color.
3. It could allow for more violence. GL obviously invented those hideously lame battle droids to avoid having the noble Jedi carving up living beings right and left. But if it'd all been b&w, that wouldn't have been nearly as gory or shocking. See: the b&w portion of the dojo fight in Kill Bill 1.
4. It would have been educational. Too many younguns these days turn their noses up at b&w. Heck, even I did back in the day. This would have compelled them to see and enjoy b&w films from an early age.
5. It could have encouraged more focus on story, dialogue, etc. How many hundreds of hours were spent on choosing the various colors of the trilogy? Hours that could have been used coming up with decent scripts. Less color-filled eye candy to show off could have forced GL to craft the best possible film, not special-effects showcase.
6. It would have been better suited to the dark tale generally. B&w film can have a nightmarish quality to it (Psycho, The White Ribbon, the dvd version of The Mist). Anakin's tragic fall to evil would have been well served by the format.
Sure, there would have been downsides. The art direction, (along with John Williams' work) is the only truly exceptional aspect of the trilogy, and much of its flavor (and thus merchandising potential) would have been lost in grayscale. (Padme's rainbow dress...

Still, for the above reasons, I think a well-done PT might have been truly awesome. It would certainly have been a bold and thought-provoking move...