diff --git a/autoload/indent_guides.vim b/autoload/indent_guides.vim
index a27529f..98c0837 100644
--- a/autoload/indent_guides.vim
+++ b/autoload/indent_guides.vim
@@ -1,3 +1,9 @@
+" Author:   Nate Kane <nathanaelkane AT gmail DOT com>
+" Homepage: http://github.com/nathanaelkane/vim-indent-guides
+
+"
+"
+"
 function! indent_guides#toggle()
   let g:indent_guides_matches =
   \ exists('g:indent_guides_matches') ? g:indent_guides_matches : []
@@ -9,17 +15,26 @@ function! indent_guides#toggle()
   endif
 endfunction
 
+"
+"
+"
 function! indent_guides#enable()
   call indent_guides#disable()
-  call indent_guides#highlight_colors()
 
+  if g:indent_guides_auto_colors
+    call indent_guides#highlight_colors()
+  endif
+
+  " loop through each indent level and define a highlight pattern
+  " will automagically figure out whether to use tabs or spaces
   for level in range(1, g:indent_guides_indent_levels)
-    let group      = 'IndentLevel' . ((level % 2 == 0) ? 'Even' : 'Odd')
+    let group      = 'IndentGuides' . ((level % 2 == 0) ? 'Even' : 'Odd')
     let multiplier = (&l:expandtab == 1) ? &l:shiftwidth : 1
     let pattern    = '^\s\{' . (level * multiplier - multiplier) . '\}\zs'
     let pattern   .= '\s\{' . multiplier . '\}'
     let pattern   .= '\ze'
 
+    " define the higlight pattern and add to list
     call add(g:indent_guides_matches, matchadd(group, pattern))
 
     if g:indent_guides_debug
@@ -28,6 +43,9 @@ function! indent_guides#enable()
   endfor
 endfunction
 
+"
+"
+"
 function! indent_guides#disable()
   if !empty(g:indent_guides_matches)
     let index = 0
@@ -39,8 +57,50 @@ function! indent_guides#disable()
   endif
 endfunction
 
+"
+"
+"
 function! indent_guides#highlight_colors()
-  hi IndentLevelOdd  guibg=#FFFFFF
-  hi IndentLevelEven guibg=#FBFBFB
+  if g:indent_guides_auto_colors
+    " capture the backgroud color from the normal highlight
+    let hi_normal       = indent_guides#capture_highlight('normal')
+    let hi_normal_guibg = matchstr(hi_normal, 'guibg=\zs#[0-9A-Fa-f]\{6\}\ze')
+
+    " calculate the highlight background colors
+    let hi_odd_bg  = indent_guides#brighten_or_darken_color(hi_normal_guibg)
+    let hi_even_bg = indent_guides#brighten_or_darken_color(hi_odd_bg)
+
+    " define the new highlights
+    exe "hi IndentGuidesOdd  guibg=" . hi_odd_bg
+    exe "hi IndentGuidesEven guibg=" . hi_even_bg
+  endif
+endfunction
+
+"
+" Takes a color and darkens or brightens it depending on whether a dark or
+" light colorscheme is being used
+"
+function! indent_guides#brighten_or_darken_color(color)
+    let percent = g:indent_guides_auto_colors_change_percent
+
+    let new_color = (&g:background == 'dark') ?
+    \ color_helper#hex_color_brighten(a:color, percent) :
+    \ color_helper#hex_color_darken  (a:color, percent)
+
+    return new_color
+endfunction
+
+"
+" Captures and returns the output of highlight group definitions
+"
+" Example: indent_guides#capture_highlight('normal')
+" Returns: 'Normal xxx guifg=#323232 guibg=#ffffff font=DejaVu Sans Mono 9'
+"
+function! indent_guides#capture_highlight(group_name)
+    redir => output
+    exe "silent hi " . a:group_name
+    redir END
+
+    return output
 endfunction