Well, I actually tried it out!  Decreasing the saturation just decreases the number of colors.  As you begin to approach B & W you get a grayscale image, adding   a hue just colorizes the same number of pixels.  In other words you just get 256 shades of blue.  Even with a tad left of colors, noticeable a color image,  you bump up against the 256 limit.  For some reason  the image I used got 236 colors even while slightly colored in what appeared to be more than just one shade, rather than just a hue if you know what I mean.  Learned something though

Thanks
Steve Cat