Final answer:
The name of the triangular diagram developed by Faber Birren to describe the relationship between a pure hue, white, and black is called the Color Triangle.
Step-by-step explanation:
The triangular diagram developed by Faber Birren to describe the relationship between a pure hue, white, and black is called the Color Triangle. It is a tool used in color theory to visualize the relationships between colors and their various shades and tints. The Color Triangle helps artists and designers understand how colors interact with each other and how they can be combined to create different effects.