I've been an illustrator for over 20 years, yet I know almost nothing about mixing paints. What I do know about is mixing process color on a computer, the color model that's used in commercial printing. Process color uses four inks -- cyan, magenta, yellow, and black -- in varying amounts to create a full spectrum of color for offset printing. I'm so used to using CMYK that I can look at a color and estimate the amounts of each of the four inks that would be used to create it. What I can't easily do is look at bottles of paint and figure out what color I'll end up with if I mix them.
In this print, I'm experimenting with mixing three colors -- blue, red, and yellow -- to see if they behave at all like cyan, magenta and yellow. Here's the red layer by itself:
And added to the yellow:
Now I'm drying the prints before I re-wet them to add the blue.