Icebergs are ordinarily blue to white, although they sometimes appear dark or opaque because they carry gravel and bits of rock.

冰山一般是蓝色到白色，尽管有时因为携带了砾石和小岩石而变成黑色或者不透明。

youdao

To appear dark or threatening, such as the sky.

黑沉沉看上去黑沉沉，具有威胁性，比如天空。

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If we could see infrared, the sky would appear dark, and grass and trees very bright.

如果我们能看见红外线，天空会看起来颜色暗淡，而绿草和树木则会非常明亮。

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The lettering will appear dark during the day, and by night will glow, with lighting hidden below the panels.

NEWYORKER: Shaping The Void

Dr Stefanov and his colleagues (or, rather, their computers) looked for the boundaries between densely developed areas, which reflect a lot of light because of all the edges and flat surfaces that people like to create, and those with more vegetation, which appear dark by comparison, as nature prefers curves.

ECONOMIST: Urban geography

Also, for no apparent reason, dark spots often appear to be accompanied by light spots.

ECONOMIST: Comparative meteorology