This design appears that the two base colors are applied bottom and top first, and then the central colour applied in whichever way it was applied, could be sponged on or airbrushed, etc.
The contrast of colors chosen would be inportant in achieving this design, note that the central colour has more black in it, which gives the illusory blend n fade.
Update - For those who say the image is fake: source of the image is ali express - these are likely a set of press on nails, the image made by the company who sold the 'fake' press on's in question. The nice design is most likely airbrush / machine.