I'm having a struggle with this, too. In a painting with overlay layers, the color picker chooses a hue which is too light. By making the layers invisible, the colors matched better, but still needed to be darkened. This was with the lighting option turned off in the color picker. On a new canvas, the color selection was accurate, so it must be a problem of that particular project. The settings for hue and saturation don't seem to make any difference whether on or off.