1. A method for adjusting a color saturation level of at least one color pixel of an input image obtained from a time varying RGB video signal, which comprises: obtaining an RGB color sample vector {right arrow over (C)} representing the color pixel of the input image obtained from the time varying RGB video signal; decomposing the RGB color sample vector {right arrow over (C)} into a white vector {right arrow over (w)} and a color tone vector {right arrow over (C)} T ; obtaining a saturation adjusted color tone vector {right arrow over (C T o )} by multiplying the color tone vector {right arrow over (C)} T by a saturation adjustment parameter; obtaining a saturation adjusted RGB color sample vector {right arrow over (C)} o by adding the white vector {right arrow over (w)} and the saturation adjusted color tone vector {right arrow over (C T o )}; and using the saturation adjusted RGB color sample vector {right arrow over (C)} o to represent a color pixel of an output image.