Turn off syntax highlighting.
Alternatively, adjust the color scheme. (https://vi.stackexchange.com/q/2995/4676)
:colorscheme (with a space afterwards) and then press Ctrl-D to list the possible completions. On my copy of Vim this shows the following colorschemes are available:
blue default desert evening morning pablo ron slate zellner
darkblue delek elflord koehler murphy peachpuff shine torte
Then just type the name of the colorscheme (e.g.
:colorscheme blue), using tab completion if you like, and voila!
If you don't like the existing colorschemes, you can install them from a third party, or even create your own.