You are not really happy, your smile is your protective color.

你不是真正的快乐，你的笑是你穿的保护色。

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The body color of the white bear is a protective color, whatever enemies are difficult to find it.

白熊的体色是一种极好的保护色，无论什么敌害，都难以找到它的踪影。

youdao

He decided to take the yellow color of the protective bands for mosquitoes inside the plant to paint the walls of the courtyard.

因为植物中蚊子的存在，他决定使用黄色来喷涂在庭院的墙以作为保护带。

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"The Color-coded Threat Level System is used to communicate with public safety officials and the public at-large through a threat-based, color-coded system so that protective measures can be implemented to reduce the likelihood or impact of an attack, " according to the DHS Web site.

CNN: Experts question U.S. terror alert system