Looking up at the sky, I caught a glimpse of the blackish dragon silhouetted dimly against the azure sky, his scales and shell being as jet-black as ever.

我仰头望天。蔚蓝色的天幕上隐约地现出淡墨色的龙影，一身鳞甲还是乌亮乌亮的。

youdao

The water was blackish.

水带着黑色。

《柯林斯英汉双解大词典》

In front of this door are 3 circles on the floor - a whitish one, blackish one, and reddish one.

门前地板上有三个圆圈-一个白，一个黑，一个红。

youdao

He stoops to loosen a heavy bunch of small, blackish Monastrell grapes from the stalk and offers me one: a syrup-sweet burst on the tongue.

BBC: The three colours of Ibiza

So the Ethiopian changed his skin to a blackish brown, which allowed him to creep up on them.

NEWYORKER: It Ain��t Necessarily So

The Ash might be salty or sweet, blackish or white.

ECONOMIST: Sai Baba