slate blue

A petrel it is, about the size of a house pigeon, and of a slate-blue colour.

Above it pulsed and banded a tumult of smoke gray clouds; the eastern horizon was a slate blue, rapidly darkening.

It reaches a length of three or four feet, and is of a slate-blue colour above and very pale yellow below.

The male is of a slate-blue, and has a broad black band across the tail.

His trousers were striped and of a slate blue colour—the "blue pants" of the ready-made clothing stores.