Most of these are not removable. You remove the speaker from the trunk area, and the grill stays in place. You may be able to remove them from behind after removing the speakers if they are clipped or bolted in place.
With a screwdriver
The 1997 Pontiac Grand Prix rear deck speaker covers are held in place by four retaining screws. Remove the retaining screws to remove the covers.
from the trunk
on what car???
You have to do it from the inside of the trunk.
The ones in the front doors aren't covers, they just look like it. You have to remove the door panel to get to the speakers. The rear deck comes off by removing the rear seat and the rear interior panels. After you do those things you can slide the rear deck off and expose the rear speakers.
Remove rear deck lid, use a 9/32 socket to remove screws, remove wires, reinstall them onto new speaker, reinstall the screws and the rear deck lid...
Begin by removing the cover from your rear speakers. Remove the rear speaker retaining screws. Remove the wiring harness from the back of the speaker. The rear speakers will come out.
Remove the cover in the rear window.
There should be a grille covering the speaker. A Flathead screwdriver can pop it off. From there, unscrew the screws holding the speaker in place, and unhook the wires. The rear deck ones are a bit more tricky You have to remove the entire back seat as well as the cover on the rear deck. The 2 speakers are located underneath. they are 6x9s.
from shop manual: remove luggage cover and holder assembly remove speaker cover retainer nut and and screws securing the cover in place over the speaker assembly loosen and remove the speaker retainer screws securing the speaker in place, lift the speaker out enough to access the wire harness at the rear of the assembly disconnect the speaker harness remove the speaker installation is the reverse of removal
REAR SPEAKER - JR41 Disconnect and isolate the battery negative cable. Fold down the rear seat backs. Remove C-pillar trim. Remove lower quarter trim behind rear seat backs. Remove fasteners from rear shelf trim. Pull out trim to access speaker. Remove speaker screws. Disconnect wire harness connector. Remove speaker (REAR SPEAKER-JR41). REAR SPEAKER - JR27 Disconnect and isolate the battery negative cable. Using a trim stick, pry the speaker grill from the trim panel. Remove speaker mounting screws (REAR SPEAKER - JR27). Remove speaker from trim panel. Disconnect wire harness connector from speaker.