Quote from Ray below:
"You can easily find a photo of their product on line and see for yourself."

Here's a link to the US early war Snyder and Short chips, with the usual disclaimer that monitors can distort the actual colors, so what you are seeing could be an approximation:

http://www.modelwarships.com/reviews/books-plans/snyder-short/usn-1/usn-1.html

Another quote from Ray:
"The 5D would serve you just fine."

From what I see on my screen, #20 Deck Gray is a little bit blue-er than 5D, but they are indeed essentially pretty close. Perhaps add "a touch" of blue to your 5D? Your call. I totally agree with the thrust of Ray's post...Even in an era of standardized paint coloration, precise matches are the exception, not the rule. FWIW.