That's a big misconception about the monitors. The original
Monitor was indeed overall black, but the majority of the dozens of others were not.
Weehawken was stated in several period documents by both Union and Confederate observers as being "lead" in color, a medium shade of gray. There were many combinations of the basic colors of white, black, lead and light gray among the
Passaic class. For example, the
Catskill had a lead-gray hull but white turret and black stack with a white band. Lehigh had a lead-gray hull and stack with black turret.
Nahant had a lead hull, black and green turret, black and white stack.