Sketchers:

I consulted with some sketchup experts on another forum, and found out that you can change the color of individual lines:

Go to the same dialog box under "styles" that Pegs was talking about, but instead of selecting Color: All the same, select "by material". Then, select all the edges you want to color, and paint them using the bucket tool. Of course you can't put a "texture" on an edge, but there is a set of "color" textures. Choose one of those. It can be difficult to click on just the edge - it's easy to miss and hit the adjacent face by mistake. "Undo" is your friend! CB.