The document discusses several diamond color grading scales used by different grading laboratories to classify the color of diamonds. The scales range from completely colorless (grade D or 0) to light yellow or brown shades (grades X, Y, Z or 10+). Lower numeric grades and letters closer to D indicate more colorless or white diamonds, while higher numbers and letters closer to X, Y, Z indicate diamonds with tints of color. The scales allow diamond experts to objectively evaluate and communicate the color of diamonds.