code: def _find_colour(particle, start_index, screen_data):
          
          _, fg2, attr2, bg2 = screen_data
          index = start_index
          for i, colours in enumerate(particle.colours):
              if (fg2, attr2, bg2) == colours:
                  index = i
                  break
          return index
docs: Helper function to find an existing colour in the particle palette.