Well, redrawing on color pages isn't really too much different than regular redraws, it's just you're redrawing on a much larger spectrum. For redrawing text, you have a good deal more leway in that you can just redraw the stuff your text doesn't cover. joining double pages can be a little difficult if there's a good size gap inbetween. The redrawing itself will take you a good deal more time because you have to constantly check to make sure things look "smooth" because colors will often vary slightly in different parts of the image.
As far as the actual redrawing goes, you'll have to play with your clone tool settings somewhat. Be sure to separate areas that touch by making a layer for each. If the area you're redrawing is a solid color, I'd just use the clone stamp with 100% hardness and 100% flow. For gradients and colors that vary over a distance, lower the flow and sometimes the hardness depending. I like to focus on areas that have consistent colors by making a pen tool selection of the area, it makes it easier to go flush up to a line. For lines, just use the pen tool, and make a selection that looks like the line, and fill it. ALWAYS put your line redrawing layers above the layers that have the fill, it makes changing/smoothing the line a lot easier to have it separate from the fill beneath it. If your lines look out of place, try using the dodge/burn/blur/sharpen/erase brush to make it match somewhat. Another trick if the line isn't a solid color ( e.g. it has some pattern because the scans are lower quality ), is to copy an area on the image that has a bigger example of it, create a pattern from it, and then overlay that pattern on the line layer.
That's sort of an overview of what I do with color pages, it's really hard to explain without making a tutorial, examples, etc of the process. No color redraws are the same, just as regular redraws, so most of it is up to the editor on how he approaches it. Lowering the flow is the key for redrawing some areas, and if you're typesetting it as well, you have a bit more leway on it. Anyway, this is just my vague methodology for it.
