The black and white photo is an interesting way to look at it. I don't mind that his bottom half is as dark as the wood, since the upper body and face really pop in that black and white photo. From the color photo, the red sash clearly stands out. However the pants are a very similar shade of brown to the wood and his cape transitions to a dark red-brown which also blends in.
There are a couple solutions I can think of...
1) Just don't worry about it, the main focus is his face and upper body and that definitely stands out. If you like it that way, then there's no need to change the piece
2) Break up that brown next to brown by either
a) Adding some clutter to the deck behind him. It's a pirate ship, no need to be orderly. There could be parchment scattered, bottles of grog lying around, bits of treasure, etc.
b) Use some light pigments to dust/dirty the pants. This can be focused along the bottom edge and then up the side so that, when you're looking from normal angles, the light pigment shows on the edge of the pants between the figure and the deck.
For either of these, you don't need something all over. Just enough to break up that edge between the two browns.
3) Repaint either the pants or the wood with a different shade. This is probably the most time consuming and the one I'd avoid... but it's still an option.
Those are just my thoughts