Many vessels would have had certain colours in common.
Decks - Most vessels (not monitors) had wooden decks. These are best painted a pale tan or light oak colour Guns - These would vary in colour from black to a dark gunmetal. Unlike the armour of ironclads, these would NOT have been allowed to rust. Rarely were bright colours used, with grey, white, brown and black being common. Most colours would fade and becoming weathered over time.The naval practice of continually painting a ship seems to have been neglected during the war, particularly by the Confederates. Ironclads would also be likely to show signs of rust to their armour, particularly close to the waterline. This would have got worse the longer a vessel spent on station.