مَرَرْتُ بِرَجُلٍ أَسْوَدَ
Translation: I passed by a black man.
مَرَرْتُ: past verb with subject tāʾ. بِ: preposition.
رَجُلٍ: genitive noun, marked by kasra and tanwīn.
أَسْوَدَ: genitive adjective of «رَجُلٍ», marked by fatḥa as a diptote.
Both noun and adjective are grammatically genitive, though their visible markers differ.