PCL Color Wheel

I get the F A C D part, but what is the last square?

There's 10 colors in the middle representing 0-9 or 1-10, but there's purple & blue in the square, but no corresponding purple color for a number.

I don't think the colors in the middle actually represent numbers, although there are ten of them. The six in the center are the test colors necessary for all four-color printing (cyan, magenta, yellow, black, white, grey). The four colors around those appear to be hues from the floral painting (maybe specific inks necessary for the reproduction).

The purple corresponds to G, or the 7th letter. The light blue is E, or the 5th letter.

FACT GE or FACT 75 - the catalogue number.

Ahhhh...