Unless they are a tan rather than a brown, it's problematic. Tonally the base colour should be lighter than the desired colour. Navy will have blue, of course, in it and black. The black fits the bill but the brown contains red and yellow and probably some green. I think the navy is going to come out muddy.
Also if it's a split suede you run the risk of some "bleed through" to the lining.
Try a spot deep in the tongue where it won't show..