Colorant print order affects trap decisions for opaque colors especially: trap direction for opaque inks is determined only by print order, and not by neutral density. You can set and/or change the order of the list of colorants.
Tip: To determine trap directions in files with many opaque colors, set the printing order using the Color Mapping dialog box in Prinergy Workshop. The color printed last defines the shape and all other colors will be pulled under it. For example, Color 1 traps to Color 2, 2 to 3, 3 to 4, and so on.