The blue of the sky paled to a light grey.

天空的蓝色渐变成了浅灰色。

《牛津词典》

The blue of the sky longs for the earth’s green, the wind between them sighs, “Alas.”

苍穹的蔚蓝渴盼大地的碧绿，微风在天地间哀叹：“唉！”

youdao

Her silk shirt dress was sky-blue, the colour of her eyes.

她穿的真丝衬衫是天蓝色的，和她双眸的颜色一样。

《柯林斯英汉双解大词典》

The curving brushstrokes of Van Gogh's expressive sky look like explosions of blue fire.

VOA: special.2010.03.24

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

The Cumberland Mountains of Tennessee rose blue-gray in the afternoon sky.

VOA: special.2009.11.14

Some 57 years later he wistfully remembered the regret at leaving the eternal snows of the Jungfrau and the sharp outline of the pyramid-shaped Silberhorn peak against the dark blue of the sky.

BBC: In Alpine villages, Hobbits lurk

The water reflected the gray-blue of the darkening sky, and the lights of the water-pumping stations had come on, making them look like a line of floating gazebos.

NEWYORKER: Great Experiment

I'm rested and relaxed after two days at this wellness-lite resort in the desert two hours east of San Diego--an effect of the vast saturated-blue sky, the 650, 000 acres of nature preserve all around, that cushy bed in my guest room, and, best of all, the laid-back approach to the mindfulness mission.

FORBES: Magazine Article