Start with two parent colors, these would be more saturated colors in your palette. In my example above I've chosen blue and orange because they're my school colors, GO ROADRUNNERS!
In the center these two colors are equally mixed at 50% in their pure saturated state. Upper center is the same mixture with white added and lower center is the same 50/50 combination with black added. Now the center right square is a 70/30 mixture favoring orange, white and black are added above and below respectively. Then I switch that formula for the left with a 70/30 mix favoring the blue.
You can use this formula with any two colors and have fun varying the mixtures to suit your needs. I did a personal challenge with this method I call "9 Sets of 9 Neutrals" where I repeated this process 9 times in oil paint using various color combinations. I was genuinely surprised at some of the colors I created and I think you will be too.
I hope this helps you on your next piece!
Sycra offers tons of awesome resources for artists on his website including an active forum community which you can check out HERE!
Stay Creative!
-Christine Lane-