red的三个实用用法总结如下：
1.paint the town red狂欢庆祝：想象用红色渲染城市的喧闹场景。
例：After graduation, we painted the town red！
毕业后我们彻夜狂欢！
Merry Christmas! Let's paint the town red.
玛丽：圣诞快乐，让我们尽情狂欢。
Miss Chen really painted the town red last week with her friends.
陈小姐上周和朋友尽兴狂欢了一把。
With so much money, we can really paint the town red.
有这么多钱，我们就能大肆狂欢了。
2.red tape官僚主义，繁文缛节；官僚作风：因为英国(包括美洲殖民地)在17世纪经常用红带子捆扎法律或官方的文件。
例：
Too much red tape slows down the process.
繁文缛节拖慢流程。
The little money that was available was tied up in bureaucratic red tape.
能用的那点儿小钱被繁文缛节拖得遥遥无期。
I've given up trying to get a visa; there is too much red tape involved.
我不想再去搞签证了，繁文缛节太多。
You have to go through endless red tape to get a residence permit. 要想获得居留许可，你必须经历无数的繁文缛节。
去除繁文缛节用动词cut (减少用reduce), 如
All ministers are agreed on the need to cut bureaucratic red tape.
所有部长都同意有必要减少官僚主义的繁文缛节。
We must cut through the red tape.
我们必须打破繁文缛节。
The new rules should help cut the red tape for farmers.
新规定应该有助于消除农民的繁文缛节。
3.red flag危险信号：字面为红旗，引申为警示危险或停止的信号或标识。
例：
A red flag slowly goes up the pole.
一面红旗徐徐升起。
Constant delays are a red flag for project failure.
持续拖延是项目失败的危险信号。
The abnormal bleeding is your body's own red flag of danger.
非正常的出血是你的身体发出的危险信号。
Then the rain came and the red flag went up to signal a halt.
然后下雨了，红旗升起示意暂停。
He kept ignoring my concerns, which was a clear red flag that something was wrong.
他一直无视我的担忧，这显然是一个明显的危险信号，表明有些事情出了问题。
Hidden state is a red flag.
任何隐藏状态都是一个危险信号。
The mere mention of his hated cousin's name was like waving a red flag in front of him.
只要一提他那个讨厌的表兄弟的名字，他就生气。
You should not take steps forward when the red flag is flying.
危险的信号出现后，你就不该向前走了。
注意：white flag（表示投降或无意进攻）白旗；承认失败并愿意停战的标志
a flag that is waved to show that you accept defeat or do not intend to attack
After hours of arguing, he finally waved a white flag and agreed to her
terms.
经过数小时的争论后，他最终投降并同意了她的条款。
They had raised the white flag in surrender.
他们已经举起白旗投降。
