Coloring With Only 6 Colors

My all time favorite coloring utensils are Copic Markers.  Copic has a challenge using only 6 colors.  You can find out about it here.  One tip that was mentioned - use Gray as the shading color.  Since I don't know much about color and shading, this was a big challenge.  I basically played with colors until I liked the shading & compatibility. You should have seen my paper!  LOL...color blobs everywhere.  I would have posted a picture of it too...only, it was trashed before I thought about it.  Anyway..my coloring:

Copic Colors:
B97
C5
E000
E00
E47
R39