I'm adding this drawing-- solid geometric object with selected edges marked for freestyle render-- but in different colors, thickness etc. (Sorry i didn't do this originally, and just saw response after Thanksgiving travel.)
I would suggest using the Material modifier for the freestyle edges.
Apply different materials to the object for the parts you want to color.
To control a property, use the Material modifier and select the material property.
Select the Freestyle Line color as you wish. I'll use the Diffuse Red channel to control the thickness and the Diffuse Blue channel to control the Opacity.
Note that the color channels can have any float value.
The green material has a Priority of 1.
Here are my notes for others trying to do this:
- Freestyle box must be checked at bottom of Render tab or freestyle line option will not show up in Materials tab.
- Render Layers tab is where you find the freestyle linesets and their linestyles, with the option to add the materials modifier.
- For the attached image I remade the geometry to eliminate seams that result from extrusion and inset tool, instead manipulating vertices directly and joining separate primitives into single object.
- The crease setting is 166 degrees.
- I also marked a few edges that weren't showing (in 3D view, mesh, mark edges for Freestyle) and checked Edge Mark box in edge types. They render in correct color for that material.
- I made a second lineset, checked only contour, and set that color (black) separately.