Monokai is a GUI-only colorscheme, originally ported to vim by Damien Gombault (first seen here).
The original repos still live, although it hasn't been updated since 2009. This repos serves only to allow monokai.vim to be installed using modern plugin managers for vim.
There's also a vim.org Script page for this colorscheme.
Add to your .vimrc:
Plugin 'lsdr/monokai'
Don't forget to :PluginInstall after editing your config files.
Fetch it over the net and store it locally in your .vim/colors folder:
$ cd ~/.vim/colors
$ curl -G https://raw.githubusercontent.com/lsdr/monokai/master/colors/monokai.vim -o monokai.vim
