This is the symbol in red:
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The symbol is tattoed on the Arashikage Ninja Clan members upon graduation.
It is the hexagram #63 symbol for Already Fording ("after completion" and "already completed" or "already done"), composed by the Ba gua triagrams for water (on top) and fire.
It originally appears on G.I. Joe: A Real American Hero #21 (March 1984) starring Snake Eyes and Storm Shadow.