Fix Modus and Kaolin themes visibility for kittens

[alternateved]

Proper fix for https://github.com/kovidgoyal/kitty-themes/issues/68 and https://github.com/kovidgoyal/kitty/issues/6320 where color15 wasn't visible for select_tab and unicode_input kittens. This shouldn't break TUI applications as https://github.com/kovidgoyal/kitty-themes/pull/85 did.

[jian-lin]

When Modus Operandi theme is enabled both in kitty and Emacs, it does not look good:

1. by default the comments are invisible
2. only highlighted comments are visible
3. background color does not look good

Before this PR, it looks good with the same config:

[alternateved]

@jian-lin Sorry, I cannot reproduce it using those themes. I've refreshed themes cache (with kitty +kitten themes --cache-age 0) and it works properly on my side with modus-themes from MELPA.

[jian-lin]

I find that the issue I mention in https://github.com/kovidgoyal/kitty-themes/pull/86#issuecomment-1573263223 is a bit tricky to reproduce.

My Emacs version is GNU Emacs 28.2 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 1.16.0, Xaw3d scroll bars) and the version of modus-themes is 20230530.627 from MELPA.

My init.el file is

(eval-when-compile
  (require 'use-package))

(use-package modus-themes
  :init
  (load-theme 'modus-operandi t)
  :custom
  (modus-themes-italic-constructs t))

This issue does not occur if I open kitty and then run one of the following commands

• emacs --fg-daemon=foo and in another tab emacsclient --socket-name foo -nw
• emacs -nw
• emacs --fg-daemon=foo and in another tab run these
  • ssh localhost
  • emacsclient --socket-name foo -nw

This issue does occur if I open kitty and then run one of the following commands

• emacsclient -nw (connect to a server started by a systemd user service)
• ssh localhost and then emacs -nw
• ssh localhost and then emacsclient -nw

Looks like it is caused by environment variables:

• environment vaiables are different between the Emacs daemon started in kitty and the one started by a systemd user service
• emacs -nw started with and without ssh localhost may have different environment variables

[jian-lin]

After checking the diff of environment variables before and after ssh localhost, I find that COLORTERM=truecolor is the root cause: starting Emacs without it causes the issue in https://github.com/kovidgoyal/kitty-themes/pull/86#issuecomment-1573263223.

So that issue is likely a config issue on my side.

Thanks!