Lordy, talk about titling at windmills.
The
http://stampplating.com/pdfs/ColorVarieties5.pdf file was first an Excel file and then save as a PDF. The original author did not include embed a separate color profile to calibrate the color in the PDF. The typical PDF 'save' down-samples the colors, so even if the Excel file colors were accurate they changed when the file was saved as a PDF.
But even if it is assumed the original PDF or website contained accurate colors, how do you your display monitor and/or printer are generating accurate colors? Have you calibrated them using the ambient lighting in your room? Neither of these things are easy or inexpensive to do.
It is one thing to make broad color statements about an image, we could probably all agree on simple stuff like that water look blue or that dress is red and not pink. But when you start trying to differentiate between really subtle hues, nothing replaces having the stamp in hand with hundreds of reference copies next to you and neutral ambient lighting.
Anyone who is working with colors needs to understand how we perceive colors and how ambient lighting impacts this, here is a simple start
https://www.pantone.com/color-intel...we-see-colorWith the basic understanding of the impact of ambient lighting to perceived colors in place the question becomes 'did Chase and Amonette or any other of the color experts define and describe their ambient lighting?'
Don
Edit. Also note that the background color a stamp is view against can
greatly influence how our brains perceive color.

The gray bar in the middle appears to be lighter in color toward the left and darker to the right, but in fact the gray bar is exactly the same color across its entire length. The background is fooling your brain into thinking it has changed. So what background is being used when folks make a color determination?