And this of all my hopes—
Repetition structure
The entire eight-line poem repeats verbatim. She's stuck in a loop, unable to move past this loss.
Bountiful colored
Past tense—the rose was colorful. She's describing something already dead, though the poem pretends to build toward that revelation.
sere
Withered, dried up. An archaic word even in 1860s—Dickinson choosing stiff, biblical language for death.
Never a worm
The worm is inside the root—invisible destruction. She's watching something die from causes she can't see or stop.