A color management system for display device includes a color management controller, a color sensor, and an advance function module configured to implement a process (a) or a process (b) applied to multiple PWM signals generated from the color management controller. Process (a) includes the steps of using a reset signal generated by and synchronized with an image signal, and a counter with special bit length and counting frequency to generate a reference signal synchronized with the image signal, and using the reference signal to synchronize the PWM signals with the image signal as output. Process (b) includes the steps of using a reset signal with special frequency and a counter with special bit length and counting frequency to generate multiple synchronized reference signals with respective different phases, and generating multiple synchronized PWM signals with respective different phases as output by the use of the reference signals.