CSS2.1中预定了17个颜色名词，他们如下：
aqua(浅蓝绿色), black(黑色), blue(蓝色), fuchsia(紫红色), gray(灰色), green(绿色), lime(鲜绿色), maroon(栗色), navy(藏青色), olive(橄榄色), orange(橙色), purple(紫色), red(红色), silver(银色), teal(凫色), white(白色), and yellow(黄色).
需要注意的地方是在CSS3中，预定义颜色名称为16个，没有了orange(橙色)。
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