Here is how I did it:
You need two shades of the same color. The darker shade ideally needs only one coat. The lighter polish should be a color that builds as you layer it. I went with OPI's Suede You Don't Know Jaques and a bottle of an iridescent nude type color. I wish I could tell you the brand, but I got it years ago (I wouldn't be surprised if it was 10+ years old) in a cheap makeup kit as a gift.
With the darker color, paint just the tip of the nail, like you would for a french manicure (yellow guideline). After that dries, use the lighter color to paint most of your nail, leaving just the moon of your nail uncovered (red guideline). Once that is dry, use the light color again to paint from the dark tip again down to the halfway point between the dark and the unpainted portion (blue guideline).
Finish up with a top coat (of course!). I use Seche Vite.
If you try this out, I'd love to see your results so please do share!