Much of her research focuses on consumer financial decision-making and health decision-making. Colby studies how people make decisions about saving and debt, how health care costs affect treatment choices, and how financial literacy training affects emotion, stress and other psychological outcomes. Her work has been presented at national and international conferences, including the Association for Consumer Research and the Society for Judgment and Decision Making, and her research has appeared in highly regarded journals including Psychological Science and the Journal of the American Medical Association.