A “D” color diamond is colorless, like a piece of glass. “E” and “F” colors are degrees of “D-ness.” When you get to “G” and “H” color you are looking at diamonds that are white like a piece of paper. “I” and “J” colors are what I refer to as “transitional” colors. That is, they are the transition from diamonds that are patently white to diamonds that are not altogether white. My perception is that “I” and “J” color diamonds are on the border between white diamonds (G and H) and diamonds that have a suggestion of yellow (K and L). So I explain that “I” and “J” colors are to white and yellow as gray is to black and white. When you see something that is the slightest bit gray, you don’t say it is black or white. That’s what “I” and “J” colors are to white and yellow. As you go down the scale, “Z” diamonds become ever more yellow.