Perl has a a lackluster colordiff wrapper for diff, but I prefer grc (generic colorizer).
With grc (generic colorizer), you can write your own wrappers for different types of commands or inputs (if you like that sort of thing).
Below, grc is running against /var/log/syslog (in the config, this file is set to a certain color scheme), where it highlights processes, pids, IPs and "connect"s.
Of course, it is recommended to use an alias so you don't forget:
alias diff="/usr/bin/grc /usr/bin/diff"
If you have git, you may just want to use that, which allows very robust diffing, even across branches.
git diff master:cogs/foo.txt branch:widgets/bar.txt
You do not have to use git diff within a repository, you can use it for just regular files.
git diff old.txt new.txt
As always, you can alias diff for ease of use.
alias diff="git diff"
