EPS vector graphics do not have a background color unless one was created in the original picture.
White areas of the graphic will display according to the box color, which is None by default. To make sure the graphic does not have a transparent background, go to Item> Modify, click the Box tab, and choose White or another color from the Box Color drop-down menu.
Jay Nelson is the editorial director of PlanetQuark.com, and the editor and publisher of Design Tools Monthly. He’s also the author of the QuarkXPress 8 and QuarkXPress 7 training titles at Lynda.com, as well as the training videos Quark includes in the box with QuarkXPress 7 . In addition, Jay writes regularly for Macworld and Photoshop User magazines and speaks at industry events.