In the Alabama case the worker had been just been told to keep away from the aircraft, then almost walked into the jet exhaust where she was warned again and then walked in front of the engine and was ingested. I doubt any amount of high vis would have stopped that, considering she'd already been seen and warned to stay away a few times.
In the Atlanta incident the worker was wearing a high vis vest, clearly visible and holding two glo sticks in the air for marshaling. Watch the video, the truck driver showed no sign he saw her, and really goes to show when there is so much light clutter around high-vis wear just joins in the background.