How to change the Google Plus nav bar color without yet-another--chrome-extension

Someone noticed my Google Plus navbar wasn't black, but a nice gray color. Here's how I did it without having to install yet-another-Chrome-extension:

1. Edit the custom.css file buried down in chrome's "user stylesheets" directory.

On Windows, go to the run window and type this line:

notepad "%userprofile%\appdata\local\google\chrome\user data\default\user stylesheets\custom.css"

This file is the style override file for Chrome. You can do other cool thing like force links to always show underlines, etc.

2. Add the following line:
#gbx4 { background-color: #F1F1F1 !important; }

F1F1F1 is the color,  you can change it by picking a different color:

3. Save. (should change immediately without reloading chrome).

[edit]

Here's a more complex Custom.css that changes the font color, mouseover color, etc:

#gbx4 {
  /* change the color of the background */
  background-color: #F1F1F1 !important;
  /* change the color of the border */
  border-bottom-color: #D2D2D2 !important;
}
.gbts {
  /* font color */
  color: #3366CC !important;
}
.gbts:hover {
  /* color of background when you mouse-over */
  background-color: #D2D2D2 !important;
}