Complex sentence: Liu Yongfu evidently had a personal preference for the colour black, having dreamed in his youth that he would one day become a'general of the black tiger', and the Black Flag Army is so named from the colour of Liu's command flags.
Split into simpler sentences: Liu Yongfu evidently had a personal preference for the colour black, having dreamt in his youth that he would one day become a'general of the black tiger'. The Black Flag Army is named from the colour of Liu's command flags.