Dan, let's start this project by working up reference sheets for the 5-color day pattern, beginning with the darker upper-surface colors. I have reviewed your WWI Aero article and you provide a table with Methuen values for this fabric. There are multiple codes for each color, though, so please confirm that I'm reading this correctly.
It looks like the table shows a Methuen range for two different samples ("Two Cloth Samples" and the "Standard Ref"). So for the Honey Yellow/Bronze color we have:
Two Cloth Samples - Honey Yellow/Bronze
Methuen Code Range - 5D6 to 5E6
Standard Ref - Honey/Yellow
Methuen Code Range - 4D6 to 5D6
Am I interpreting the table correctly?
Also, I'm familiar with the WWI Aero Symbol system for keying the colors to the correct lozenge (using letters A - E) but what is the significance of the number give in the first column? Or the letter given in the first column of the lower-surface colors?