dict_1 = {'A': ['red', 'red', 'blue'],
          'B': ['red', 'green'],
          'C': ['blue', 'green'], ....}

dict_2 = {'A': Counter({'red': 2, 'blue': 1}),
          'B': Counter({'red': 1, 'green': 1}),
          'C': Counter({'blue': 1, 'green': 1}), ....}

fraction = {'A': [2/3, 1/3],
            'B': [1/2, 1/2],
            'C': [1/2, 1/2], ....}

fraction = { key: [v/len(colorz)] for namez, colorz in dict_1.items()
                          for name, color in dict_2.items()
                          for k, v in color.items() }