In "Tangerine," why did Erik and Vincent spray paint Paul's eyes?

Erik and Vincent spray-painted Paul's eyes because they believed that Paul was the one who got Vincent into trouble. Essentially, both boys accused Paul of telling on Vincent for spray-painting the gray wall at the Silver Meadows development. Paul was only four or five-years-old at the time of the incident.

Paul denied ever exposing Vincent for his part in spray-painting the wall. However, both boys had resolutely ignored Paul's pleas at the time. While Erik held Paul's eyelids open, Vincent sprayed white paint into them. This horrifying incident left Paul screaming in pain on the garage floor. Paul remembers his mother trying to clean his eyes out with the hose. He was then taken to the hospital, where the doctor warned that Paul might lose his peripheral vision. Despite the overwhelming odds against Paul, the doctor assured his parents that Paul would not be blinded by his ordeal.

To prevent Paul from hating his brother, Erik, for his cruel actions, Paul's parents later made up a story about how Paul's vision impairment originated from staring too long at a solar eclipse.