Adding to the previous tip on multi-color lines there is a much more convenient way when all you need is a 2-color dashed line!

In Corel DESIGNER X5 you can apply halos not only to callouts, but also to any curve or geometric (line) object.

Since the halo can be generated with a color, you can use the halo of a curve as background, with a dashed line as foreground color element of your 2-color dashed line.

1. Create the curve and apply the desired dash/dot line type to it.
2. Add a halo to the curve - you'll find the halo settings in the Properties tool bar with the curve selected:
   
    
    
3. Aligning the halo width to the outline width of the curve and giving it a color you will produce a 2-color dashed line
   
    

You can edit the curve with any Shape tool as it's still one single curve object.