Need to return values from class method using reflection

In my Winform the user has the option to pick sets of colors depending on the button clicked.

The colors themselves are stored in a different class. Using reflection the Method that is called depends on the the button clicked while all buttons use the same event.

Code in form:

private void Button_Theme__Click(object sender, EventArgs e)
{
    Button button = sender as Button;
    string[] Color = Regex.Split(button.Name.ToString(), "_");

    Type thisType = this.GetType();
    ColorTheme ColorTheme = new ColorTheme();
    MethodInfo ColorMethod = thisType.GetMethod("ColorTheme.Theme_" + Color[2]);

    Color[] ColorThemes =  (Color[])ColorMethod.Invoke(this, null);
    ColorThemeLight = ColorThemes[0];
    ColorThemeMedium = ColorThemes[1];
    ColorThemeDark = ColorThemes[2];     
} 

Code in the class:

public Color[] Theme_Yellow()
{
    ColorThemeLight = Color.FromArgb(255, 255, 255, 200);
    ColorThemeMedium = Color.FromArgb(255, 191, 191, 150);
    ColorThemeDark = Color.FromArgb(255, 127, 127, 100);
    Color[] Colors = { ColorThemeLight, ColorThemeMedium, ColorThemeDark }; 
    return Colors;
} 

I am getting the following error but i can't seem to pinpoint where the problem lies and how to fix it.