The color intensity scale shown here is created in acrylic painting. Any pair of complementary colors could be used to create the intensity scale.
Color intensity is gradations between two complementary hues or two split complementary hues.
Color intensity scale is explained in more details in the color wheel movie under:
Color Wheel Theory
Date Painted: 2009
Painting Width = 8 inches (204 mm)
Painting Height = 11 inches (280 mm)