More straightforward then the last two, the intent of the the caffeine line is direct, obvious and intense, as caffeine should be. The shape not only evokes the awoken eye, but also its dilated pupil, communicating a sensation of surprise, alertness. In short, something is happening and it's happening NOW.
Yellow is the color of the sun; our warmest and most important source on energy. Both qualities should be associated to BRST Caffeine if it's ever to be considered as a replacement for one of the day's coffees.