The study focused on 11,472 patients who hadn’t refilled their generic drug prescription for up to 10 days. The researchers compared these delinquent patients with 50,050 patients who refilled their generic prescriptions regularly. Patients whose medication had changed color were 27 percent more likely not to refill it than were people whose pill color hadn’t changed. More than half of patients diagnosed with epilepsy did not refill their drug prescriptions if the pill color had changed.

“Pill color is one of the things that policymakers should look at when they’re trying to figure out ways of addressing this epidemic of non-adherence,” Kesselheim said.

The study had limitations. The researchers examined only antiepileptic drugs, which aren’t as widely used as other medications. Also, the researchers didn’t determine whether the color changes affected the health of patients.