How to programmatically change theme colors?

Question

i need both design and programmatically change the theme any one help.... with sample code

Answer 1

(App.Current.Resources["PhoneAccentBrush"] as SolidColorBrush).Color =
Color.FromArgb(12,12,54,145);
(App.Current.Resources["PhoneForegroundBrush"] as
SolidColorBrush).Color = Colors.Green;
(App.Current.Resources["PhoneBackgroundBrush"] as
SolidColorBrush).Color = Colors.Purple;