I'm using Golden acrylics for my miniatures wargaming hobby and have been struggling with color mixing to get reasonably close to historical colors for 20th century military vehicles and uniforms. After reading a bunch of threads here in color theory I tried something.
I copied the color I was aiming for into Adobe Illustrator (I have CS5.5 Master Collection in case a different Adobe program would be better for this) and put the document into CMYK color space. Then I started pasting in some Golden colors from their website (of colors I [thought] I owned).
Then I found this linear algebra equation solver website: http://mkaz.com/math/linear_algebra/...alculator.html
This website will only calculate for CMY, no K, but I'll address this later.
I put in the Golden color CMY eyedropper tool results on the left of the equals sign and the CMY of the color I was trying to match to (1973 "Sinai grey" for IDF armored vehicles - CMYK: 33.33, 35.29, 44.31, 1.18 (%)) on the right of the equals sign and solved.
For most of my trials I had Titan Buff as the third color. Obviously, I rejected solutions where one of the variables was negative. My first viable solution came to Cobalt Green Titanate, Quinacridone Magenta and Titan Buff in about equal parts. This is when I learned that I did not own all three colors in the same format (heavy body, fluid, airbrush) and I didn't want to fool around with figuring how to measure proportions of heavy body to fluid. So I brought up some other reds that I had.
Then I had a realization. The color I was aiming for was closer in value to white than black*. In fact, I had started using Chromium Oxide Green, but ended up getting bunches of negative solutions until switching to the Cobalt Green Titanate. So I tried using Light Magenta as my "red" (I'm reading about CMY, but my default thinking is RBY and I have doubts about CMY not obtainable from RBY but that is not for this thread). The solution came up almost equal amounts green and red with a tiny bit Titan Buff.
This is when I looked at the K channel for the colors. The K for my target color was actually a bit higher than the average of my green and red, so I decided to omit the Titan Buff and hope that pigment mixing saturation (brightness?) loss would be my friend. Equal amounts of the two colors was a bit too pink, so I added a bit more green and got reasonably close to where I wanted to be. I think I then added too much Glazing and/or Airbrush Medium, but that isn't germane to color theory.
I mentioned the lack of K channel in the aforementioned equation solver. Ideally, one could solve for the four parameters or, as artists, just add some neutral grey as needed if the value was way off.
So, my idea was that using CMYK color definitions of colors with a little bit of linear algebra would get me to a good starting point for a color match. I then experienced success with this. I also learned some things about color while doing this, even if more mathematical / numerical than paint on substrate.
In fact, I just had a pigment thought. During this whole process I was concerned that using the CMYK color space intended for printing would not be very applicable to paint mixing as printing uses discrete dots of separate colors to achieve blending, similar to airbrushing (my only college art was airbrush so I tend to see everything as how it relates to airbrush). But, thinking about it, paints have discrete pigment particles and if the paint is thoroughly mixed, these pigment particles will be homogeneously (evenly) distributed, thus simulating a printer or airbrush putting down the various pigment particles that have been mixed as paint.
* I wonder if this is a chroma question rather than a value question, as most of my negative solutions seem to have been related to one of my mixing colors having 100% Y channel. I also wonder if the method I used will give better results for colors that do not have any channel at 100%. The intuition I have about this is that 100% for a given channel is akin to blowing out an individual color channel in digital photography.