mypy ignores color_output=true if there is no tty, but in a CI context color is often supported and desired even though there's no tty. pytest solves this with a tri-state flag: --color=yes/no/auto, where color=auto is equivalent to mypy's color_output=true, and color=yes forces color on.

chad$ pytest --help | grep color
  --color=color         color terminal output (yes/no/auto).

I'm happy to submit a PR for this if you think it makes sense.

There is the issue of backward compatibility. We have a few options

• introduce a new flag --color=yes/no/auto and deprecate the old boolean one. This would let us maintain backward compatibility for a few versions while people switch over
• change the type of --color-output/--no-color-output to enum string. This would break backward compatibility, at least for the CLI. We might be able to hack something to work for config files.