code: def _update_preview(self):
          
          color = self.hexa.get()
          if self.alpha_channel:
              prev = overlay(self._transparent_bg, hexa_to_rgb(color))
              self._im_color = ImageTk.PhotoImage(prev, master=self)
              self.color_preview.configure(image=self._im_color)
          else:
              self.color_preview.configure(background=color)
docs: Update color preview.