Bug 56637 [Preferences] DialogMessageArea image is too large
Is the background color of the error shown by DialogMessageArea to be changed? Or do you intend to leave it as it is right now? The error message looks a little out of place in the current implementation (being surrounded by white space).
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferenceDialog.java
* <p>
	 *
	 * @param b <code>true</code> to include a Help button, 
	 *  and <code>false</code> to not include one (the default)
	 */
	public void setHelpAvailable(boolean b) {
		isHelpAvailable = b;
	}
	/**
	 * Set the message text. If the message line currently displays an error,
	 * the message is stored and will be shown after a call to clearErrorMessage
	 * <p>
	 * Shortcut for <code>setMessage(newMessage, NONE)</code>
	 * </p> 
	 * 
	 * @param newMessage the message, or <code>null</code> to clear
	 *   the message
	 */
	public void setMessage(String newMessage) {
		setMessage(newMessage, IMessageProvider.NONE);
	}
	/**
	 * Sets the message for this dialog with an indication of what type
	 * of message it is.
	 * <p>
	 * The valid message types are one of <code>NONE</code>, 
	 * <code>INFORMATION</code>, <code>WARNING</code>, or <code>ERROR</code>.
	 * </p>
	 * <p>
	 * Note that for backward compatibility, a message of type <code>ERROR</code>