Do you want to display some code in a Keynote presentation?
It's easy. All you need is Homebrew installed.
First you need to install the program highlight.
$ brew install highlight
So you have a piece of code. For example some Python code. The take that snippet of code and save it to a file like code.py. Now all you need to do is run this:
$ highlight -O rtf code.py | pbcopy
Then, switch back into Keynote and simply paste.
But if you don't want to create a file of the snippet, simply copy the snippet from within your editor and run this:
$ pbpaste | highlight -S py -O rtf | pbcopy
The -S py means "syntax is py (for python)".
You can use highlight for a bunch of other things like creating HTML. See man highlight for more tips.