Emerging organic light-emitting diode (OLED)-based displays have drastically different power consumption when displaying different colors, due to their emissive nature. They bring a new opportunity for power saving by transforming GUI colors. In this work, we study this opportunity using a commercial-off-the-shelf QVGA OLED module and user studies. We present techniques that adapt GUIs based on existing mechanisms as well as arbitrarily under usability constraints. Our measurement and user studies show that more than 75% display power reduction can be achieved with user acceptance. Categories and Subject Descriptors D.2.2 [Design Tools and Techniques]: User Interfaces General Terms Algorithms, Measurement, Human Factors Keywords OLED Display, Graphic User Interface, Low Power