AquaPurpleButton from code, http://highvaluecode.com.au/creating-custom-wpf-controls-from-code

AquaPurpleButton.cs

using System.Windows.Media;

namespace PurpleButtonLib
{
    public class AquaPurpleButton : PurpleButton
    {
        public AquaPurpleButton()
        {
            Background = Brushes.Aqua;
            BorderBrush = Brushes.DarkCyan;
        }
    }
}