Now, the mood is darkening.

现在，他们心情忧郁。

And the growth outlook is darkening.

而且经济增长前景也不光明。

Two elephants lurk in the darkening room.

两个强劲的对手潜伏在昏暗的屋子里。

And the outlook for foreign sales is darkening too.

出口销售的前景也黯淡了。

It's generally harmless but can cause permanent skin darkening.

一般而言，这种情况无碍健康，但会导致永久性的肤色变暗。