I have found that many of the "imperfections" in some of the comics here (like color/printing errors) are what make the books so interesting and so much more intriguing than reading a re-touched and corrected classic title that loses it's comic-book-feel. For example, there are some titles here (many of the "True Crime" books) where the colors are off because it was inked in great detail and then sent to color somewhere else most likely, where they could not or did not take the time to make it precise.
It is certainly true that in some cases, the artists drew and inked in greater detail than the lousy printing could do justice to. I suspect that this accounted for artists like Alex Toth who ended up going for a simplicity of line and stark spotting of blacks. It ended up looking good even with lousy printing. I doubt that
where the coloring was done had much to do with the quality. Again, aside from sheer hack coloring (ala Fawcett or Charlton), most off-register coloring was due to the printers.
I will say that I think there were some coloring preferences at some comic publishers (such as ACG) where they didn't do the art much justice. ACG seemed to lean towards yellows and yellow-greens and pinks and other pastels, often undercutting the mood or genre of the stories. This is one of the things that made EC seem so superior. Their coloring was largely excellent.