A color transformation method includes following steps. First, a color signal is received. Then, a saturation calculation step is performed to generate a saturation value of the color signal, and a hue-angle-weighting calculation step is performed to generate a first hue-angle weighting of the color signal corresponding to a first LUT and a second hue-angle weighting of the color signal corresponding to a second LUT. Next, a color calculation step is performed to transform the color signal into a first color output signal according to the saturation value and the first hue-angle weighting and to transform the color signal to a second color output signal according to the saturation value and the second hue-angle weighting.