VIM SYNTAX HILIGHTING

vim does syntax hilighting based upon filetype. e.g., 
vim myfile.c 
will edit the file using C syntax hilighting because
the file ends in .c. Vim understands many filetypes, 
including:
.sh (bash shell)
.jav (java)
.py (python)

vim uses the file name to detect filetype (e.g.,
myfile.sh  myfile.jav )
vim also understands that if the file starts with
#!/bin/bash
it is a bash shell program.

If vim does not do the syntax hilighting you wish,
you can manually set it from within a vim session
with :set  (or :se for short) as in:
:se syntax=sh

Alternately, you can tell vim to treat this file as
if it has some other filetype, with:
:se filetype=c (or :se ft=c for short)


VIM COLORSCHEMES

Set colorscheme in vim with :colorscheme. e.g.:
:colorscheme koehler

You may loop through the various colorschemes as follows:
type :colorscheme followed by a space followed by the tab key. 
Each time you hit tab it shows another colorscheme.
You must hit enter for that particular colorscheme to show. 
If you don not like it, repeat (:colorscheme space tab) and pick 
another colorscheme. Obviously (?) you can set a colorscheme 
directly, if you know the name, e.g.,
:colorscheme pablo