I fans of less package since it available on most operating system (except windows!) and I can open / read large log with (ANSI color) file so fast and you look like hacker on terminal..LOL
But to read the source code, less -r don’t help much for syntax highlighting. So as alternative I use source-highlight package.
$ sudo apt install less source-highlight
then add this lines on your ~/.bashrc file
# less RAW (remove ESC chars)
export LESS='-R'
# without line number
alias lessh='LESSOPEN="| /usr/share/source-highlight/src-hilite-lesspipe.sh %s" less -M '
# with line number
alias lesshn='LESSOPEN="| /usr/share/source-highlight/src-hilite-lesspipe.sh %s" less -nNM '
Now reload you bash session with source ~/.bashrc and you are done! There is also a package called python-pygments which is depend on python dependencies. It has more input language but rather slower.