When you Image Trace, using the default black and white tracing preset and expand - the black and white are grayscale. When you double click the fill in the toolbar to choose a new color for the black or white, the resulting color is a shade of gray. Then, you have to go to the Color panel and change the sliders to a different color model to be able to see the color you chose. It would be easier if the black and white were aligned with the document color mode, RGB or CMYK instead. You don't encounter this issue if you apply color from a saved swatch, only when using the color picker.