Words: Feeling a bit green!
Don't be sick!
Ever felt that wave of nausea wash over you, leaving you pale and unwell? How would you describe that feeling of queasiness, that sense that you might be sick? It's like your complexion has taken on a sickly hue, isn't it?
Think of it this way: You're visibly unwell, perhaps a little faint, and the colour seems to have drained from your face.