Yes eating blueberries can cause your poop to become dark in color or black which is very normal and nothing to worry about.
If the poop goes back to normal color after you stop eating blueberries then it's the blueberries that are causing your poop to become dark or black.
If the poop continues to be dark or black then it can caused by some other medical condition that a doctor can test you for.
Some other things such as licorice, lead, iron pills and bismuth medicines like Pepto-Bismol can can also cause dark poop or black poop.
Beets and tomatoes can also make your poop look red and seem like the presence of blood when actually it's the beets or tomatoes causing the red looking poop.