If the color of the foam topping is light, it means that the espresso has been underextracted, probably because the grind was too coarse, the water temperature too low or the time too short.

• 如果说这层泡沫的颜色太浅，代表这杯浓缩咖啡萃取得不足，原因可能是咖啡磨得不够细致、水的温度太低，或是时间太短。