Also available for Stack Exchange and Hacker News
Any color or user changes are displayed and saved as soon as you make them.
All settings are saved and synchronized through browser sync.
You need to have the browser sync enabled in order for this to work. (Chrome, Firefox)
Modify this extension in any way you want. To get to the source code simply extract the extension.
Rename the extension file to .zip and extract it.
This add-on was co-written by Petr Janeček.