This plugin allows to print files with syntax highlighting (according to vim syntax rules and colorscheme). Applying syntax rules to a big file may be slow.
It only works with NeoVim, because --headless options is required to prevent vim from using the terminal.
bin/catcolored.sh $FILENAME — print the file with colors.
bin/catcolored.sh +'set ft=json' - — print json from stdin with colors.
Use a plugin manager:
Plug 'Vftdan/nvim-catcolored'