<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_darker_color(self):
 """The color of the clicked version of the MenuElement. Darker than the normal one."""

        # we change a bit the color in one direction
        if bw_contrasted(self._true_color, 30) == WHITE:
            color = mix(self._true_color, WHITE, 0.9)
        else:
            color = mix(self._true_color, BLACK, 0.9)

        return color