With this plugin, a WordPress site Administrator can set some default options for new user accounts. All new users registered on the system will inherit these settings. The following user defaults can be set:

• Enable/Disable Rich Text Editor
• Enable/Disable Comment Keyboard Shortcuts
• Administrative Interface Color
• Public Display Name Format

NOTE: This plugin only affects newly created user accounts (after the plugin's activation). Existing user accounts will be unmodified.

From WordPress.org: Go there. Click "Download"

or

With Git:

cd [wordpress directory]/wp-content/plugins/ git clone git://github.com/sant0sk1/wp-user-defaults.git