I'm assuming they just didn't care, and given how altered the colors were and how disorganized working for Lucas supposedly was, I believe that it's very possible that some people may not have even been sure what was and wasn't meant to look a certain way.

I'm not sure about the errors. They very well could've been creative choices because as we've seen with the SE's, George's creative decision-making process is flawed to say the least. As for them being fixed in the blu ray, Lucas has been known to make changes to the movies, and then go back in and change the changes either back to the way they were, or alter them further.

I'm not trying to defend the color job on the DVD's just because I know an acquaintance who worked on them. I think the deal was that he worked in a horribly frustrating environment with a man who was completely passionless, but still obnoxiously stubborn, about everything related to the movie he was selling, but I think it had more to do with Lucas' bad ideas than anything else. It's been so long since this conversation, but I think he said something along the lines of, "Lucas got what he wanted," regarding the colors, and maybe that's just a big cop out, but knowing how ridiculous everything related to Star Wars has been since 1997 I'm completely willing to believe it.