How to say: subway line is not in operation
今天部分蓝色地铁线路中止/暂停运行。

Operation has a lot of similar meanings. But 操作 is not appropriate here since it's usually used with machines or computers. For a subway line, 运行 is much better because 行 means moving. 运营 is OK but it's usually used for companies or long term activities.

And in Chinese there is no predictive so you need to add a predicate like 停止、中止、暂停.