The top represents 256 colors going from pure green (on the RGB scale) to pure blue. How many different colors can you see? Can you name them all?
On the bottom, is a scale with 256 increments going from "clear" (white) to very dark blue. How many shades do you see?
For relative simplicity, I'll say the top goes from green to green aqua to aqua to blue aqua to blue. Where would you draw the line to divide up each of those colors?
The price guide defines 8 "color depths", clear, tint, ice, light, "medium" (no descriptor), dark, royal, blackglass. Where would you draw the line for each of those?
While I am not speaking for Don, I believe the price guide has in the past, and does, use the "consolidated color" system (CC) This maps "similar colors" into a single color name, even if you can see a difference in those two colors. No different than the "consolidated design" system (CD) where similar shapes, even if you are able to see a slight difference between them, are mapped to a single CD number.
As they say "further detail is left to the speciality collector". If you want to collect the whole rainbow of colors from green to blue, go for it! If you can see the difference between each color you have, you can put together a nice run of colors.
You can start in the middle with Aqua. Blue Aqua Aqua Aqua Aqua Aqua Aqua Aqua Aqua Aqua has just a shade of Blue compared to Aqua. Blue Aqua Aqua Aqua Aqua Aqua Aqua Aqua Aqua is a little more blue, Blue Aqua Aqua Aqua Aqua Aqua Aqua, a little more, until you get to the "consolidated" color "Blue Aqua". You can repeat the naming convention on the other side is you wish! :)
Of course, we have to take into account what colors I'm able to see vs. the colors you can, as well as what light we are looking at them with. The Kelvin "K" temperature of the lighting. Tungsten, cool white, warm white, "natural light", 5000K, sunlight, shade, and on and on...
No wonder we can never nail down a color!