This is a great introductory/practice worksheet, or even formative assessment worksheet/printable for students to practice and/or demonstrate understanding of how to create the illusion of a 3-D sphere using colored pencils.

This worksheet has six empty circle shapes, with different instructions on how to color/shade the forms using colored pencil:
1 - coloring in the direction of an object
2 - varying pencil pressure to create value
3 - using complementary colors (layered) to create value
4 - using black colored pencil (layered over color) to create value
5 - using a graphite pencil to show value/form
6 - "blank" circle for additional practice or repeat favorite technique

I am happy to answer questions or help you to use any of the resources in the "Make Art Be Happy" store - just let me know!