Will the model be displayed in a way that both sides are visible, or just the camo'd side?

If both sides will be visible,try and find a ship that has the same pattern as on Breckonshire's port side and see what pattern this ship has on its starboard side. Then, using that starboard side pattern as a precedent, paint Breckonshire in a similar pattern.

If, on the other hand, only the camo'd side will be visible on display, do what Tim has suggested and paint the starboard side grey.

You could always offer to paint a camo pattern for your customer if, or when, evidence comes to light.