Maybe this will help, Tabitha. When I want to mix a very specific color, I condition the clay with my pasta machine and roll out the various colors in sheets of the same thickness. Then I use a small cutter to cut several circles from each sheet. That way I have a lot of little circles that are exactly the same amount of clay. Then I start mixing them. It's a lot quicker and easier to mix small amounts of clay than to mess with large quantities. The really cool thing with this technique is that, once you have the color you want, you can go back and count the number of circles you have left versus the number of holes in the clay sheets, and you will know the exact recipe. Then you can replicate it easily. If you used 8 little circles of beige, one circle of pink, and two circles of white (for example), you can use a whole block of beige clay, 1/8 of a block of pink, and 1/4 of a block of white the next time you want to mix a batch. I like Judith's suggestion of making a sample and writing the recipe on the back.
Like you, I mix most of my colors without recipes, but I don't make figures where I want to use the same colors over and over. Since I am an architect, I do have a "blueprint blue" recipe that I wrote down for some pieces I don't have in my shop yet.
Good luck!