Hull is 5-N Navy Blue...
The 'gray' that most people think all warships were painted in was pre-war Gray, and then again after WW2, post war Haze Gray.
5-N was introduced because the Navy felt it would make ships more difficult to see. Of course, throwing a 1/4 mile wake while doing 30+ knots kinda defeats that altogether.
The 5-N you're adding is the pure color, meaning, that's how it looks right out of the can. Obviously, some dry brushing and weathering will lighten it up a bit, they do tend to fade.
Here's a picture of Lexington II (CV-16) in the same Ms 21 scheme you're doing.
Regards,
Jeff Herne
Modelwarships.com