Chris Appleton is a celebrity hair artist and Global Artistic Director for Glam Seemless (often colorful hair extensions). His work (often temporary) can be seen on the Jenner/Kardashian women, Jennifer Lopez, Ariana Grande, Katy Perry and more.
In February 2018, he turned Kim Kardashian's hair pink. According to Chris's Instagram post, "I used Manic Panic mixed with conditioner. The conditioner dilutes the Manic Panic so we could achieve a perfect pink! The key to this look is getting the right pink for your skin tone! Try colored pink sprays before you commit!" (See link 3 below for this quote and post.)
See more pink hair bef-afters (including Kim's sister Kylie) via links 1 and 2 below. See Chris's Instagram posts on this treatment via links 3 and 4 below. Finally, see a link to the Manic Panic website via the last link.