A simple port of @sainnhe's fantastic sonokai Vim colorscheme to iTerm2 (ported directly from his Alacritty colors).
Download whichever variation you prefer (or, better yet, download them all) from iTerm2/ and open the .itermcolors file(s) in Finder to import into iTerm2.
Select the newly imported colorscheme from Settings -> Profiles -> Colors -> Color Presets.