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 sky was just a little lighter blue than his suit, clear and even with only one cloud in it, a large, blinding white one with curls and a beard." Notice that image of the cloud, the blinding white cloud.

天空比他身上蓝色的西装颜色更亮，更清朗，甚至,空中只有一朵白云，是大而亮白的螺旋状和,胡须状，注意这多云的图像，一朵亮白的云。

耶鲁公开课 - 1945年后的美国小说课程节选

The problem with the Blue Sky Laws was that they were each state done separately and it was hard for states to manage what were, basically, national businesses.

蓝天法的问题在于,各州的法律都是分开制定的,由各州政府去处理,然而全国性的问题却无从解决

耶鲁公开课 - 金融市场课程节选

There are different theories about why they call them Blue Sky Laws.

至于为什么把它叫做蓝天法,有很多不同的说法

耶鲁公开课 - 金融市场课程节选

So the Blue Sky Laws were basically coming in the teens.

所以蓝天法仅上世纪初被广泛使用

耶鲁公开课 - 金融市场课程节选