• Button with hand-selected colors. Highlight is brighter and less saturated than the face, and shadow color is darker and more saturated.
  First button
• Button with outset/inset using face color. This illustrates that the outset/inset color is used as the highlight, and the shadow is calculated from it — so this button appears to have no highlight (it does, but it's the same color as the button face).
  Second button
• Button with outset/inset using hand-selected highlight color. Because the highlight is relatively desaturated, so is the shadow, which looks wrong. (It also doesn't introduce quite enough contrast.)
  Third button
• Button with outset/inset using a new highlight color that's lighter than the button face color, but the same saturation. This looks better, but in my opinion, not as good as the hand-selected colors - this highlight is too saturated and the shadow too desaturated. It looks like it's being lit with a green light, rather than a white one.
  Fourth button