As I always do for these types of gradients, I started with the lighter of the two shades as a base for each nail - in this case, blue for the first and middle fingers, pink for the ring finger, and mauve for the pinkie., Next, after applying cuticle barrier, I applied the gradient using makeup sponges. The only problem with a spectrum gradient like this is the number of sponges you'll end up using - one for each finger - but it's worth it in the end. As you can see, I only used five shades, but it ends up looking more nuanced than that because of the pairings on each nail. To finish, I removed the cuticle barrier and crisped up the edge with a clean up brush dipped in acetone.

For the stamping, I reached for the Beauty Big Bang 04 Stamping Plate, which has this great mountain of skulls image, along with What's Up Nails Neither Noir Stamping Polish. I always love the look of rich black stamping over a bold rainbow gradient because I feel like it really pops that base. I also applied the same image to all of my nails because I didn't want to get too busy or intricate and take away from the base.