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@Gourmet Hawaiian Kava . He can give you some Isa for testing. Or buy it from N@H.
The problem with the color cards, is that color is two dimensional. (Three dimensional, technically, but it can be reduced to two useful dimensions) Think of the "color pickers" in computer applications:
See
http://www.labnol.org/home/hue-saturation-luminosity/20104/
The "hue" is the x-axis of the color square, and the saturation is the y-axis.
The problem with kava, is that for noble kava, the
hue is pretty well defined. In the CIE color diagram it lies along a straight line. But the
saturation is variable. Here's the part of the CIE color diagram that includes the acetone test colors:
View attachment 6706
Points along the green line are noble kavas. They have the same hue, but different saturation. So the problem with making a set of comparison cards is: what saturation should you pick for the "noble" on the card? And what saturation for the "tudei" color, and "adulterated" colors? You can only pick one of each.
What you really need is an inexpensive colorimeter that can measure the hue electronically.
I've been looking into making such a thing using colored LEDs and photodiodes.
Please stay tuned...it might be a while since I have an actual job, too...