How to assign different colors to splines viewable in the viewport? When importing a .dxf architectural drawing I get all lines drawn in a dark green color. (however they had been assigned unique colors in autocad)

Is there an option to change the appearance of one or more line colors to achieve a better organized scene? (preferably in the viewport without any additional modifiers.)

In the past I've imported several .svg files but they always seem to turn out as a black outline in the viewport.

I wasn't able to find much documentation about this subject.

Machine specs:
Windows 8.1
Blender 2.78a
Renderer: Cycles
I see that if you give the curve object/spline a tiny bit of Depth, then you can set a material to it and see it in viewport. I have exaggerated the Depth here and set it to 'Full' but you can see here what is going on. If the spline does show a color in the imported material, possibly it will show after giving it some depth.