def METHOD_NAME(self, view=None):
    """This method is called immediately before each draw.
    The *view* argument indicates which view is about to be drawn.
    """
    if self._changed['pos']:
        self.pos_buf.set_data(self._pos)
        self._changed['pos'] = False
    if self._changed['color']:
        self.color_buf.set_data(self._color)
        self._program.vert['color'] = self.color_buf
        self._changed['color'] = False
    return True