2 inches. According to official website of Yunnan Open University, the 2023 graduation certificate photo of Yunnan Open University requires a 2-inch blue background photo, and lipstick and other makeup colors that affect the real appearance, including hair dyeing, are prohibited. Yunnan Open University is a school sponsored by the Yunnan Provincial People's Government and headed by the Provincial Department of Education, adhering to the concept of openness and lifelong service.