Great looking drawing!
Did the USN really paint its ships light grey in the civil war?
Yes. Both sides experimented with camo. The South apparently used some tans/browns for their ironclads plus blues and grays. Blockade runners sometimes sported grays. The Union used blacks, grays apparently graphite colors.
Note that the black may have been graphite paint which can colorshift depending on lighting conditions! We found that out while doing 1800's color interpretation for some museum projects. The email strings amongst the experts was heated and fun. The in-person gatherings turned into geeky, drunken, hilarious free for alls that transformed the period color knowledge base for that community.
A bunch of the monitors sported an assortment of striping colors on turrets and smokestacks to tell them apart. Look up the Passaic class I did some time back...from reliable sources.
USS Comanche may have been white overall.
I also believe a number of the mass produced gunboats had ID stripes done. Will be looking into and drawing in the future.
Currently working on Confederate Ironclads. There will be more color, very few black ones.