The display is wrong when using iTerm2 + screen + emacs on macOS monterey

Question

When I use iTerm2 + screen + emacs, the display is something wrong. For example, underline is set automatically at whitespace even if I don't customize setting. And character's color is different from what I don't use screen. The color is pink on screen + emacs, but default color must be blue. There is a different behavior between using screen and not using screen.

each information I use as below

• GNU Emacs 28.1
• Screen version 4.09.00 (GNU) 30-Jan-22

And if I checked list-colors-display in this state, colors are not displayed correctly.

If I don't use screen, the display looks good and list-colors-display is shown correctly.

And if I use terminal.app instead of iTerm2, it also looks good.

Please tell me how to display correct on iTerm2.

Answer 1

I found the workaround. If I used emacs 27.1, I don't face this issue.

Answer 2

iTerm2 sets COLORTERM environment variable to truecolor that makes emacs think it can use more colors than 256 - which screen doesn't support. Just unset COLORTERM and things should work as expected.

Answer 3

adding below line:

setenv COLORTERM ""

to my ~/.screenrc solved the issue for me.