Serialisation of Class to XML is leaving Blank Values

Hard one to explain, can anybody spot what is wrong?

I am serialising a class to XML, but one of the properties (A public Class within the Class) is being given blank values in the XML.

I am creating my own Settings Class which i am serialising to XML and deserialising back into a class onload of the application.

I have put debug points into the Save method and the "ColourScheme" does have values but they are being blanked in the XML.

public class SettingsModel
{
    // DECLARE: Settings File Location
    private static string SettingsFilePath = String.Format(@"{0}\{1}\{2}", Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "Typhoeus BluePrint", "BluePrint_Settings.xml");

    // DECLARE: Public Settings
    public DateTime LastUpdated = System.DateTime.Now;
    public string StylesheetName = "style.css";
    public string WebPageName = "index.html";
    public string ProjectDirectory = String.Format(@"{0}\{1}\{2}", Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "Typhoeus BluePrint", "Projects");
    public ColourSchemeClass ColourScheme = new ColourSchemeClass();

    public SettingsModel()
    {

    }

    public void Save()
    {
        LastUpdated = System.DateTime.Now;

        // DECLARE: File Stream Object
        FileStream fs = new FileStream(SettingsFilePath, FileMode.OpenOrCreate);

        // DECLARE: Serialisation Parameters
        XmlSerializer ClassSerialiser = new XmlSerializer(typeof(SettingsModel));

        // SERIALISE: This Class to XML
        ClassSerialiser.Serialize(fs, this);

        // CLOSE: File Stream
        fs.Close();
    }
}

Here is the ColourScheme Class

public class ColourSchemeClass
{
    #region Objects

    // DECLARE: Colour Scheme Properties
    public Color BaseColour = ColorTranslator.FromHtml("#1E1E1E");
    public Color HighlightColour = ColorTranslator.FromHtml("#414141");
    public Color SelectedColour = Color.White;

    #endregion
    #region Constructors

    public ColourSchemeClass()
    {

    }
    public ColourSchemeClass (Color Base, Color Highlight, Color Selected)
    {
        BaseColour = Base;
        HighlightColour = Highlight;
        SelectedColour = Selected;
    }

    #endregion
}

Here is the XML after serialisation. (Extract because I can't seem to format it here) (Replaced Tag open and close with square brackets)

[ColourScheme]
[BaseColour/]
[HighlightColour/]
[SelectedColour/]
[/ColourScheme]