glass reflects, it has no colour.
if the boat is on the ocean, the glass would reflect sky or water depending on your angle of view.
I might paint the 'glass' a sea green with a horizon line of white (fading upwards).
the glass area itself would be fairly small. the porthole frames eat into the area.
on the outside of the hull, you cannot really see anything of the brass porthole doors and frames.
- just the inner frame around the porthole opening.
all the frame and hinges would be internal.
everything is brass, and would have been polished for aesthetics.
However, the oval portholes swiveled at a center pivot, and they appear to have a painted frame around the glass.
This might have been white or black depending on the location?