Set Line Intensity to 100 and click Render . This will enhance the lines. Click Render Scene again and set Aspect Ratio to 100. Click Render . You can now see how the thickness of the lines vary according to their direction.
Horizontal lines are thicker than vertical ones.
Now let us color the drawing. Open the Material Editor , if it was not already open, and click the first sample slot to make it active. Click the Diffuse color swatch and choose any color you like for the sphere and the teapot. Now click the second sample slot where you should have the material that has been assigned to the box. Again, click the Diffuse color swatch and choose any color you like for the box.