Colour can also be used to convey specific meaning such as warning (red), caution (yellow), safety (green), etc.

颜色可能并且被使用表达具体意思譬如警告(红色)，小心(黄色)，安全(绿色)，等。

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The safety identification marks for fuel gas pipeline facilities, such as mark stake, test stake, mile stake, warning board, etc. ;

标志桩、测试桩、里程桩、警示牌等燃气管道设施安全识别标志；

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