Bitmap Tracer Dialog Box - Trace Mode
This drop-down list lets you specify the maximum number of colors in the final object. The color depths available are:
Monochrome - 2 colors
Grayscale - 256 shades of gray
256 color - 256 colors
Photographic - 16 million (24 bit) colors
Selecting more colors than exist in the original bitmap wastes memory and is not recommended. The only time increasing the colors is useful is when tracing a heavily dithered 256 color bitmap and you want near-photographic quality.
Each of these modes has its own set of parameters which are all saved using the Save Settings button.