[Qgis-user] Black/White and colors maps

[Shane]

   I have the need to create two maps; one with color and the other 
black and white.  The color map has trails (in several shapefiles) with 
each trail a different color.  The other map has the same trails (same 
shapefiles) but each trail is represented as a dashed black line.

    The brute force way to do this is to add two layers of the same 
shapefile (with different layer names of course).  Then in the 
Properties of each layer, modify the line style as needed.  I've done this.

    What about using the "Data defined properties ..." button in the 
simple line style properties dialog?  Is that possible?  But I don't 
understand how I would trigger the selection of the required style.

    (I'm using QGIS 2.6.  Yes I know, a dinosaur, but it's working.)

    Shane