Install elpa-rainbow-mode by entering the following commands in the terminal:
sudo apt update sudo apt install elpa-rainbow-mode
Description:
colorize color names in buffers
This minor mode sets background color to strings that match color names, e.g. #0000ff is displayed in white with a blue background.
Homepage: https://elpa.gnu.org/packages/rainbow-mode.html
Version: 0.13-1
Section: universe/lisp