These variations are more muddied and organic than when only 2 colors are mixed. Here are few additional suggestions when mixing your own colors.
Start with the lightest color and add the stronger color to it. Emperor's Silk will easily become dominant to just about any other Chalk Paint color. It's best to add in small amounts, until you are satisfied. This helps avoid too much of a color.
Mix 2 colors thoroughly before adding a third color.
Start with small measurements and keep a record of your results. You can always make
more as long as you know the quantities. Best to make only the amount you will use.
Keep any extra paint in a securely closed container. I use Mason Jars, but you also can use plastic as long as it has a tight seal. There is a shelf life to Chalk Paint and I like to prolong it. Although you can add water if it becomes too thick, once it dries out completely there is little you can do. Never let it freeze- I store all my paints inside, not just Chalk Paint.
If you are considering painting one of your favorite pieces in a mix of English Yellow, Emperor's Silk, and Napoleonic Blue, here are some Pinterest photos to inspire you.