求助：怎样写出一个红色的下划线

灌水区

```latex \color{red}{\_} ``` 效果：$\color{red}{\_}$
by 徐晨轩✅ @ 2024-04-14 13:28:22

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`$\color{red}{\_}$`
by Igallta @ 2024-04-14 13:44:45

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``` \color{red}{\_} ``` 效果：$\color{red}{\_}$
by xiangzhenze611 @ 2024-04-14 13:52:31

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Thanks @徐晨轩 @[Iam_God](/user/813622) @[xiangzhenze611](/user/1005749)
by Pacyd5 @ 2024-04-14 14:43:15

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此贴结
by Pacyd5 @ 2024-04-14 14:44:00

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`\color{Red} \underline{y=kx+b} ` $\color{Red} \underline{y=kx+b} $
by C_plus_plus_12345 @ 2024-04-21 08:27:08

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