Blackish

His knee turned a ghastly blackish purple from the swelling.

That fig has a blackish color.

The slime was blackish and smelly.

In winter, the crown is white, but there is a blackish patch about the eyes, and the bill and feet are dark.

On Donald's planet, the plants are blackish.

Hác Sá (Black Sand) is the most popular beach in Macau. The sand is indeed a grey to blackish colour and makes the water look somewhat dirty (especially at the tide line), but it's perfectly clean.