Well, Stila says you don't have to. They created Custom Color Blushes that are supposed to morph into the perfect color for you as they react to your skin.
Stila makes two blush colors in this formula, and pink and a coral, and one bronzer. I haven't tried the bronzer, but I have both the blush colors to show you.
Stila says: This perceptive one-shade-fits-all powder blush reacts with your skin's pH to create a one-of-a-kind, customized shade perfect for you!
These are very finely milled and soft and only takes a few light strokes with a brush to get a beautiful flush of color.
The pink looks scarily bright in the pan, and a heavy swatch makes it look like a crazy bright purple based pink, but when it is blended it turns into a sheer, light cool pink. This color is completely matte.
Stila Custom Color Blush in Pink
Stila Custom Color Blush in Coral
Now, I don't really know if these truly adjust to the ph of the skin to give a custom color, but the do apply sheer enough that they will look good on many skintones. They have a wonderfully smooth texture and do give a beautiful natural flush to the cheeks.