In the beginning, and the middle, and the end, as always, there was the Puerto Rican flag: countless thousands of them waving as the National Puerto Rican Day Parade marched and danced up Fifth Avenue in Manhattan on Sunday in the steady drizzle, flags worn as ponchos, flags adorning T-shirts and hats and flip-flops.

But there was also a different version of the flag on display this year: black and white instead of red, white and blue, stripped of color to remind spectators — and anyone in Washington who might have been watching — of the parade’s grim backdrop: the destruction and continuing aftermath of Hurricane Maria, and what many view as the federal government’s inadequate response to the disaster.

And there was another new symbol, emblazoned on banners and T-shirts: a number, 4,645, representing a recent estimate by public-health experts on the hurricane’s death toll on the island, far in excess of the official death toll.