I hand mix many of my colors. The color wheel helps give the general direction but there's a lot of variables to consider. Amount of resin, amount of pigments, type of pigment, etc. One important lesson I learned is that white does NOT brighten a color. It will wash it out and turn it pastel. Also keep in mind that even if you do small trial pours to get a color that when you go to make a larger batch that not all pigments will scale evenly.
I think for what you're asking you might want to try and search for custom car paint formulas or for the program that companies like Lowes or Home Depot use in the paint mixing machines.