Yesterday you told me about the blue blue sky.

昨天你还告诉我，天空是那么蓝。

youdao

Blue flies into the sky, so the sky is blue.

蓝色飞入天宇，所以天空是蓝的。

youdao

What is blue? The sky is blue.

什么是蓝色的？天空是蓝色的。

youdao

This was because all you could see was the very blue sky and the very hot sun.

VOA: special.2009.01.14

Maybe it could refer to either the poet or the sun throughout the entire line, if you think of the mantle blue as being the actual sky that the sun is able to twitch over his shoulder.

或者两者皆可,从整句的行文看来，如果你们把蓝色的丝巾看作是真实的天空的话,那么太阳的确是能够在他的肩上轻轻颤动。

耶鲁公开课 - 弥尔顿课程节选

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

The baked brown cliffs and the clear blue sky were joined by the tinge of green on the sandstone rocks for the first time, in my memory.

FORBES: Setting an Innovation Agenda for the Ocean: The Next Frontier for People Like Us

The bright yellows of the recently harvested corncobs and the bright blue Chinese sky contrast sharply with the grays, browns and smudged greens of the flat, bleak, open countryside.

NPR: Chronic Water Shortages Hit Rural Chinese Hard

Maybe the most appropriate salute to the survivors came when the last flying Lancaster bomber trundled heavily through the blue sky over Green Park and dropped thousands of poppies.

WSJ: Bomber Command Memorial | They Were the Means of Victory | By Richard Holledge