From the announcement:
Due to the deep distrust the Japanese Army and Navy had for each other, joint operations were all but out of the question and the Navy created the Special Naval Landing Forces as a result. First seeing action in 1932 during the ‘Shanghai Incident’ of the Sino-Japanese War, the SNLF were highly trained, high quality troops with excellent morale. Each SNLF formation was named after the base in which it as formed.
Naval troops wore uniforms of a similar cut to those of the Army, but in olive drab rather than the Army’s khaki and with black rather than brown boots. This makes a unit of SNLF stand out nicely from the Army units in your force, adding greater variety as well as no mean performance.