Corel Draw has some real problems with transparencies sent to a printer. A color shift behind a transparency is the result. There are a couple of ways around this.
One is to do all of your bitmap overlay work in Corel Paint and import the results as cpt files. The other is to flatten transparent images in Corel Draw into a single bitmap.
Drop shadows are especially vexsome in Corel Draw. They always print with a weird color shifted rectangle. I've taken to duplicating an object, converting the duplicate to a bitmap, editing that bitmap in Paint adding a drop shadow there, separating the shadow, deleting the object, and returning the drop shadow to Draw. Clumsy but it works.