Right again, Pete, thanks. About the skin, It looks great. I found a couple of bad pics I had, but I'm afraid there's not much more. The 3 S-55 that arrived to Mallorca from Orbetello on august 19th, 1936, were those inmatriculated MM45167, MM45173 and MM45175. They stopped at Pollença to refuel and arming and then attacked the Republican millitias at Porto Cristo. The next day, while the S-55 were at Palma de Mallorca's Port, they were attacked by Republican S-62, which bombed them, damaging one, that remained while the other two came back to Italy the 21st.
The damaged one was repaired as shows this picture:
If the plane retains the scheme that had during the brief combats, it looks like no distinctive was showing, may be they were hidden before departing from Italy to avoid conflict, or may be they were covered by new paint while repairing.
What we know is that after repair, it was painted in this scheme. Here at Palma de Mallorca's port, some months later:
Black bands were painted on both hulls and...under the wings? (That's weird isn't it?). On starboard hull, the new name was painted: "Mañana por la mañana", an ironical jocke, since every day the mechanics were asked when the plane would be repaired, they answered "tomorrow morning".
About the bands on the wings, I think the logical would be that they were painted over the dorsal face of the wings, like they were in many other seaplanes. For instance, in this crashed Spanish Cant Z-501:
A detail
BTW, interesting scheme for a skin, isn't it?