fade

The bright red curtains began to fade after hanging in the direct sunlight for a year.

(Chinese) 鲜红色的窗帘在阳光直射下挂了一年后开始褪色。

The sound of the train's whistle slowly faded as it moved further away into the distance.

(Chinese) 随着火车向远方驶去，汽笛声渐渐消失了。