Oh, sorry! I wasn't very clear, was I?
The soldiers on Alcarillo's ship should be in service to the King of Gondor - so their uniforms, insignias should be the traditional white on sable.
In reference to Eorl of Rohan - the colors mentioned in his post for the Gondorian guards need to be changed, as white on blue (or silver-white on blue) were the traditional colors for the Lord of Dol Amroth.
So, no changes needed, Dunwen
~*~ Pio