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》

That's because the ambient light (in this case the blue sky) gets bounced of pretty much everywhere specially the Shadows.

那是因为环境光(蓝色的天光)被更多的反弹，尤其在阴影的部分。

youdao

The color is magnificent, with the cobalt blue sky in the background and the warm light on the lion.

背景中钴蓝色的天空和狮子身上暖色调的光线，颜色好极了。

youdao

But a clear, cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more easily than they do red light.

BBC: rainbow