CompuServe Messages

When I want to print one color over another (i.e., black type over solid blue background), is it important to reverse out the blue from the background where the black type will go? Does this cause registration problems? Is it important to reverse out the type when a lighter background (i.e., yellow) or a screened background (i.e., a 25% screened blue) is used? Thanks for any advice on this… -bg