At either end of the straight line we have the descriptions "Vivid" and "Dull" . This line is called the iso-hue line. There is another straight line that intersects the iso-hue line. This is called the iso-chroma line. At either end of this iso-chroma line, we have a display of symbols, In Fig. 2, these are "BG" and "B" . The hues are staggered in circular pattern or loop starting with red and going through orange, yellow, yellow-green, green, blue-green, blue, purple-blue, purple and purple-red and ends with red again.