Configuration for seamless transition between light and dark modes. See video https://youtu.be/TSSkUD7vY00.

.zshrc

# CHANGE THE COLORS TO THE RELEVANT ONES FOR YOUR COLORSCHEME
fzf() {
  if grep -q dark "$HOME/theme"; then
    FZF_DEFAULT_OPTS="$FZF_DEFAULT_OPTS --color=fg:#e0def4,bg:#2a273f,hl:#6e6a86 --color=fg+:#908caa,bg+:#232136,hl+:#908caa --color=info:#9ccfd8,prompt:#f6c177,pointer:#c4a7e7 --color=marker:#ea9a97,spinner:#eb6f92,header:#ea9a97" /opt/homebrew/bin/fzf
  else
    FZF_DEFAULT_OPTS="$FZF_DEFAULT_OPTS --color=fg:#575279,bg:#fffaf3,hl:#9893a5 --color=fg+:#797593,bg+:#faf4ed,hl+:#797593 --color=info:#56949f,prompt:#56949f,pointer:#907aa9 --color=marker:#d7827e,spinner:#b4637a,header:#d7827e" /opt/homebrew/bin/fzf
  fi
}

config.lua

local uv = vim.loop

-- trim function, taken from http://lua-users.org/wiki/StringTrim
function trim6(s)
  return s:match '^()%s*$' and '' or s:match '^%s*(.*%S)'
end

-- taken from https://github.com/nvim-lua/plenary.nvim
local read_file = function(path, callback)
  uv.fs_open(path, "r", 438, function(err, fd)
    assert(not err, err)
    uv.fs_fstat(fd, function(err, stat)
      assert(not err, err)
      uv.fs_read(fd, stat.size, 0, function(err, data)
        assert(not err, err)
        uv.fs_close(fd, function(err)
          assert(not err, err)
          callback(data)
        end)
      end)
    end)
  end)
end

-- CHANGE THIS TO THE FILEPATH YOU'RE USING
local themepath = "/Users/ml/theme"

function adjust_theme()
  read_file(themepath, vim.schedule_wrap(function(data)
    if trim6(data) == 'light' then
      vim.opt.background = 'light'
    else
      vim.opt.background = 'dark'
    end
  end))
end

adjust_theme()

local fse = vim.loop.new_fs_event()
vim.loop.fs_event_start(fse, themepath, {}, function(err, fname, status)
  if (err) then
    print("Error " .. err)
  else
    adjust_theme()
  end
end)

themechange.sh

#!/bin/sh

if [ $# -eq 0 ]; then
  if grep -q dark "$HOME/theme"; then
    theme=light
  else
    theme=dark
  fi
else
  theme="$1"
fi

# CHANGE THE THEMES TO THE ONES RELEVANT TO YOU
if [ "$theme" = "light" ]; then
  kitty @ kitten themes "Rosé Pine Dawn"
  kitty @ set-colors -a "$HOME/.config/kitty/Rosé Pine Dawn.conf"
  echo 'light' > "$HOME/theme"
else
  kitty @ kitten themes "Rosé Pine Moon"
  kitty @ set-colors -a "$HOME/.config/kitty/Rosé Pine Moon.conf"
  echo 'dark' > "$HOME/theme"
fi