此外，天然染料往往是浑浊的颜色而且它们很快褪色。

Further, natural dyes tended to be muddy in hue and fade quickly.

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“黄”这个字描述的是其河水浑浊的颜色。

The word "yellow" describes the muddy water of the river.

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天然牙的视觉外观除了颜色的三要素色相、明度、饱和度以外，还有许多第二光学特征：半透性、浑浊度、晕色、表面光泽度、荧光性，其中以半透性最为重要。

In addition to value, hue and chroma, there are many subtle secondary optical properties of natural human tooth, such as translucency, opacity, iridescence, surface gloss and fluorescence.

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