There are two significant photographs of HMS Laurentic (1) on the web. One was taken from off the starboard bow and shows the ship in dark livery. possibly black hull with dark grey upperworks; the other photograph was taken from a camera off the port side and shows the ship broadside on in overall light grey. Light grey was adopted by the Royal Navy across the board by 1917 taking over from dark grey of the 1914-16 period. HMS Laurentic had been re-fitted early in 1917, so the photograph of the ship in light grey would have been taken of the Laurntic shortly before she sank. Unfortunately, shadows cast by the Sun make it difficult to see the guns but close examination of the photographs suggest that David's interpretation is a good guess for the ship in dark grey, except at the stern, and unshielded 6in guns were probably in the open in the breaks in the superstructure aft of the bridge and aft of the mainmast. Pictures of Megantic show that these areas of the weather deck are clear except for stays for the masts. The early photograph show the possibility of an unshielded gun on the starboard side against the forward face below the bridge, but this may be a crane. It is impossible to see any guns at the stern of the ship in this photograph because of the angle off the starboard bow of the camera and it is impossible to find unshielded guns on the forecastle because of booms, deck clutter and the camera looking upwards to the decks of the ship.
The later photograph shows box-like structures on the after part of the forecastle and on the top of the structure at the stern of the vessel (a docking bridge?) I think these would be shielded 6in guns.
Those of you who are sceptical about the fitting of shields to guns on auxiliaries at this time should look at summaries of the operational logs for this ship and you will see that Laurentic was highly regarded as an AMC and was used as the main escort vessel for convoys to tropical destinations in 1917.
The wreck of Laurentic lies in Eira teritorial waters and the wreck is privately owned. A number of Irish diving clubs have visited the wreck and photographed their visits. On one of these visits, an unshielded 6" gun is visible and it was salvaged and brought ashore. The wreck is badly damaged because it was transporting gold when she was mined and sank and I have been unable to determine which gun has been recovered. A number of photographs of Justica have been included among the dive photographs, so be careful over interpreting the photographs.