Complex sentence: The skin color of both male and female is generally dark brown (contrasted with the usual dark brown or red for males and light brown or white for females)--this could merely be convention, or it may depict the "life" blood.
Split into simpler sentences: The skin color of both male and female is generally dark brown (contrasted with the usual dark brown or red for males and light brown or white for females). This could merely be convention, or it may depict the "life" blood.