人体内有三种色素,包括血红素、红色素和黑色素。血红素只出现在人体的血液里面,而红色素和黑色素则存在于人体的皮肤表面。黑色素如果不刺激它的话可能不会明显地出现,可是如果经过阳光和紫外线的照射会把它诱导出来。所以在热带的地区人的皮肤颜色就比较深,甚至是黑色的,寒带由于缺乏阳光,所以那里人的皮肤也就比较淡。热带地区的肤色属于暖色系,而寒带地区的肤色为寒色系,其余地区的肤色则称中间色系。颜色与人的精神拿一天之中的时辰来区分,暖色系的人包括了清晨型和黄昏型,而寒色系的人包括了午后型和黑夜 There are three kinds of pigments in human body, including heme, red pigment and melanin. Heme only appears in the body’s blood, while the red pigment and melanin are present on the human skin surface. Melanin may not noticeably appear without stimulating it, but it will be induced if exposed to sunlight and ultraviolet light. So in the tropics people’s skin color is relatively deep, even black, frigid zone due to the lack of sunshine, so the human skin there will be relatively light. The skin color in the tropics is a warm color, while the color of the frigid zone is the cold color, while the color of the rest is called the middle color. Color and the spirit of the day to distinguish between the time, warm-blooded people include early morning and evening type, while the cold-color system includes the afternoon and night