Colour matching is absolutely vital if they are to look natural. Things you should look out for to make the files match. For detailed explanations on video editing with VirtualDub see the articles I have written in the advanced VirtualDub section. Sometimes there will be too much colour flair in the image and reducing the saturation a bit helps. The unsharp mask filter gives us the most control here and is probably the one to use.
Specials usually have more noise than original movies.
Using such filters as the 2D cleaner can do wonders in this area. You probably will not need to adjust all of the above, but these are the things to look out for. Try each filter and compare the cut scene with the original. Ideally we want frame by frame accuracy. But as you know this will corrupt your Divx so you must edit from keyframe to keyframe.