A display device and a color adjustment method thereof and a method for displaying video signals are provided. The display device includes a video signal receiver, a scaling engine, a color engine, an output stage, and a panel. The video signal receiver receives the video signals. The scaling engine is coupled to the video signal receiver to modulate the resolution of the video signal. The color engine is coupled to the scaling engine, which includes a local adjusting unit. The local adjusting unit adjusts hue, saturation, or intensity of a group of pixels, and thereby increase the quality of images. The output stage is coupled to the color engine, which outputs the adjusted video signals. The panel is coupled to the output stage, which displays the adjusted video signal.