cygwin .zshrc to make mintty change background color after each time you start zsh

zshrc.sh

# This goes in ~/.zshrc

typeset -A bgcolor_to_next_color
bgcolor_to_next_color=(
	# The darkest IBM Carbon colors from https://huetone.ardov.me/
	22,22,22 7,25,8
	7,25,8   8,26,28
	8,26,28  6,23,39
	6,23,39  0,17,65
	0,17,65  28,15,48
	28,15,48 42,10,24
	42,10,24 45,7,9
	45,7,9   22,22,22 # loop around to the beginning
)

set-next-mintty-bgcolor() {
	current_color=$(grep '^BackgroundColour=' ~/.minttyrc)
	current_color=${current_color/BackgroundColour=/}
	next_color=${bgcolor_to_next_color[$current_color]}
	if [[ $next_color = "" ]]; then
		next_color=22,22,22
	fi
	sed -i -r "s/BackgroundColour=$current_color/BackgroundColour=$next_color/g" ~/.minttyrc
}

quietly-set-next-mintty-bgcolor() {
	# Don't print e.g. "[2] 4262"
	setopt local_options no_monitor
	# & to run without slowing down startup by 80ms
	set-next-mintty-bgcolor &
	# Don't print "[2]  + done       set-next-mintty-bgcolor"
	disown
}

quietly-set-next-mintty-bgcolor

Padding= in ~/.minttyrc can also be useful in not having terminals visually bleed into each other:

In your ~/.minttyrc file add a line that says:

Padding=8

This adds an 8px border on the inside of the window frame for all subsequently launched mintty terminals. Of course you can change the 8 to whatever size appeals to your eyes.

https://stackoverflow.com/questions/51675382/set-border-width-for-mintty-window-on-cygwin-windows-10