There was a small patch of blue in the grey clouds.

乌云中透着一小块蓝天。

《柯林斯英汉双解大词典》

"It is a gray day." "Yes, but dinna ye see the patch of blue?"

“这是个阴天”“不错，但你难道没有看见也有补丁似的几片蔚蓝的天空吗”？

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The blown-out Windows of a blue building at one of the street and a burnt patch of grass on a roundabout hint at the unrest.

一条街道上蓝色建筑中烧毁的窗户和在环形交叉路口小块焚尽的草地暗示着动荡的局势。

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Financial analysts see a patch of blue sky should car sales recover.

FORBES: What GM Will Look Like, If It Survives

Find this orientation by looking through the crystal at the sky at a time when you can see the sun, mark the sun's direction on the crystal, and your mark will always point towards the sun when you match the beams from even a tiny patch of blue in an otherwise overcast sky.

ECONOMIST: How Norsemen found their way round in cloudy weather