Blue spots are a common characteristic of Veileds. It actually means that something is causing them stress/ irritation. My boy always shows his dots when I take out my bearded dragon and he catches a quick glimpse of her. Generally if these dots persist then it means something needs to change. But chameleons get stressed out easily and can even be caused just from a humans presence. It's sometimes hard to pin-point what exactly causes the stress, but if he isn't showing those blue dots all day long I wouldn't worry too much about it