The leaves start off green but turn red later.

树叶起先是绿色，到后来会变红。

《牛津词典》

The maple trees turn brilliant red in autumn, adding another dimension to the colors in the harvest season.

枫叶在秋天变成了鲜红的颜色，为丰收的季节增添了另一抹色彩。

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The colours are magnificent, but the question of exactly why some trees turn yellow or orange, and others red or purple, is something which has long puzzled scientists.

这些颜色很瑰丽，但究竟为什么有些树会变成黄色或橙色，而有些树会变成红色或紫色，这个问题一直困扰着科学家。

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The leaves turn colors of red and gold and then die, falling to the ground.

VOA: special.2009.11.09

They may have a high body temperature and some areas of skin may turn red.

VOA: special.2009.05.26

In fact, they get green tomatoes sprayed with ethylene gas to make them turn red.

FORBES: Magazine Article

The phytochrome can then be exposed to a different shade of red light to turn the gene off.

FORBES: Cyborg Yeast Have Their Genes Controlled By Computer

"First, modern maize pollen grains are larger and turn red when stain is applied, whereas ancient grains do not, " they said.

BBC: Maize was key in early Andean civilisation, study shows