Select paths
File: AI 1-2.ai
You select individual segments of a circle, copy them, and paste in front. You then create a special effect by stroking the four new segments with different colors.
 
Create a circle. (Hold down the shift key as you draw to make sure it is a perfect circle)

Choose the direct selection tool

 
Move direct selection tool to the edge of the circle/. You should see a black square appear at the bottom right of the arrow.

Right click. Make sure you can see something similar to this drawing.

You have now selected just the top right quarter of the circle.

Copy this section (Edit>copy)

Paste a copy in front of the original (Edit>paste in front)