The 6" wide walls (6" wide x 8" high x 16" long) come in 4 colors - Grey, Tan, Buff, or Chocolate.  The 6" wide walls don't require any columns for reinforcement, and offers the same look as an 8" wall.  Any columns wanted would be by design or preference. The 6" wall is built the same as an 8" wall.  It has the same footing, and the same vertical reinforcement.  The difference in cost between the two wall systems is the cost of the materials.