the combined effect of a person's hair, skin, and eye colour

Their colouring is so totally different that you would never think they were sisters. 她们的头发皮肤颜色大不相同，你绝对不会想到她们是姐妹。

a substance that is added to food or drink to change its colour artificially

It says on the label that no preservatives or artificial colourings have been added. 标签上说没有添加任何防腐剂和人工色素。