Flexible electroluminescent devices have sparked widespread interest due to their tremendous applications in bioinspired electronics, smart wearables, and human-machine interfaces. In these applications, it is important to reduce the operating electrical frequency and realize color modulation. Herein, flexible electroluminescent devices have been fabricated with phosphor layers by a solution method. Using polyvinylidene difluoride as a dielectric layer and ionic hydrogels as electrodes, the devices can be effectively driven even when the operating frequency is 0.1 kHz. More importantly, the devices can exhibit multi-color emission, including blue, green, red and white. The results show that the developed devices are promising for flexible optoelectronics.