I think it was because people were overselling investments and saying, there's no limit to this investment but the blue sky above.

我想这是因为,当时人们过度宣传投资产品,并宣称,投资收益无止境,如头顶的蓝天那么遥远

耶鲁公开课 - 金融市场课程节选

One person says, "I think the wall should be painted blue."

一人说，“我觉得这墙应该刷成蓝色。”

I agree课堂 - SpeakingMax英语口语达人