The idea is to replace the #000000 with the color of your choice. If "default" is white, you could run

echo -ne 'e]11;#ffffffe'

Now since OP wants it in a bash script, I adapted the script by blueyed available here https://gist.github.com/blueyed/c8470c2aad3381c33ea3

#!/bin/sh

# Query a property from the terminal, e.g. background color.

#

# XTerm Operating System Commands

#     "ESC ] Ps;Pt ST"

#

# Source:

# Adapted from https://gist.github.com/blueyed/c8470c2aad3381c33ea3

# Posted at:

# https://stackoverflow.com/questions/2507337/how-to-determine-a-terminals-background-color#7767891

#



# save stty

oldstty=$(stty -g)



# Such that no input is needed for the read command:

stty raw -echo min 0 time 0



#11 for background color

printf "033]11;?033"



# xterm needs the sleep

sleep 0.1

read -r answer



# Change background color for #fff000 (as an example)

printf  "033]11;#fff000033"



# Do your stuff on yellow background

# Here for purpose of demonstration just sleep

sleep 1

#

#

#



# Restore background-color.

printf "033$answer"



# Restore stty

stty $oldstty

You can then put your actual code in this script and modify the custom bg color (here yellow) and the sleep times etc. I tested it only on gnome-terminal.