It means something like a kind of dulled grayness or ordinariness of life.

它代表着一种,生活的灰暗，单调。

耶鲁公开课 - 文学理论导论课程节选

What values does he embody? Grayness grayness that suggests the color of a land and a culture, the color of stone, of peasant clothes.

体现了什么品质，灰色,灰色暗示了,一种土地和文化的颜色，石头的颜色，农民衣服的颜色。

耶鲁公开课 - 现代诗歌课程节选