:syntax on

Set permanently in .vimrc:

syntax on

Turn on or off color syntax highlighting in vi or vim.

tldr;

To those who are considering using vim, my recommendation is to use MacVIM, NERDTree, PeepOpen (or command-t), and use the mouse, arrow keys, and familiar OSX’isms all you want. Very quickly, it will become obvious that there’s a better way to do all kinds of things, and you can pile on the newly found efficiency once you’ve successfully made the switch without losing the ability to do work in the short-run.

via Everyone Who Tried to Convince Me to use Vim was Wrong « Katz Got Your Tongue?.