They weren't really black, but time conflates color and infamy in the heart.
Battle of the Equator, 1927 (also called First Terawaki). The Crown Fleet sees its darkest day, somewhere above the Pacific.
As arms became more potent, stealth replaced the might of massed fleets. The Equator was a sharp turning point, seeing the Pyrrhic victory of the massed English fleet against the German pickets which sought to keep them from making the steam needed to break away from Earth's gravity. The Emperor of Mars made orbit, but the Empress of Luna was lost to the sea. The defeat was for both technological and tactical reasons, though these both would take time to learn. With the loss of this grand vessel, relief of Phobos was in doubt and both sides burrowed deeper into the red tunnels of Mars in anticipation of a long siege.
Note: This was done with Corel Painter 2017. In-universe the image was painted by Kismet Clarke for the Imperial Times. He also has a small part in the