This plugin is used for displaying thin vertical lines at each indentation level for code indented with spaces. For code indented with tabs I think there is no need to support it, because you can use :set list lcs=tab:\|\ (here is a space).
This plugin takes advantage of the newly provided conceal feature in Vim 7.3, so this plugin will not work with lower versions of Vim.
To install the plugin just put the plugin files in your ~/.vim (Linux) or ~/vimfiles (Windows).
If you use a plugin manager you can put the whole directory into your ~/.vim/bundle/ directory (Pathogen) or add the line Bundle 'Yggdroot/indentLine' to your .vimrc (Vundle).
You can change the color of indentLines:
for Vim, set g:indentLine_color_term in your .vimrc, e.g. let g:indentLine_color_term = 239,
for GVim, set g:indentLine_color_gui in your .vimrc, e.g. let g:indentLine_color_gui = '#A4E57E'
for none X terminal, set g:indentLine_color_tty_light and g:indentLine_color_tty_dark in your .vimrc. e.g. let g:indentLine_color_tty_light = 7(default: 4), let g:indentLine_color_dark = 1(default: 2).
You can also change the indentLine char:
for both Vim and GVim, set let g:indentLine_char = 'c' where 'c' can be any ASCII character. You can also use one of ¦, ┆ or │ to display more beautiful lines. However, these characters will only work with files whose encoding is UTF-8.
If you think this script is helpful, follow the GitHub repository, and don't forget to vote for it on Vim.org! (vimscript #4354).
