It usually has to do with the amount of lighting, colors that you're wearing.

它通常与照明的数量，你穿的衣服的颜色有关。

To test how nocturnal lighting color affects mood, the researchers exposed hamsters to nighttime conditions of no light, red light, white light or blue light for four weeks each.

为了测试夜间光颜色如何影响心情, 研究者们将仓鼠放到没有光, 红色光, 白色光或蓝色光的夜间条件下进行各4周的研究。