It wouldn't be such a bad idea if there weren't IDEs that would help you review your code more easily.

Think of a text document you would scan for typos. Sure it would help you to print it out and read it on paper. But finding them with words auto correction is much faster.

This kind of auto correction is also present in IDEs (integrated development environment / the program you use to do the actually coding). You can also jump from one part of your code to another part for a quick lookup or analyze it with its help.

So printing it out not only doesn't let you editing it it also slows down reviewing / debugging / refactoring it.

and apart from what the others said, if you'd decide to print the code for some reason, printing colored text on black background would be pretty wasteful way to do it

Likewise - it's only happened a few times in my life, but there have been moments in a 2k-line long SQL stored proc I inherited that I needed to print the thing off and user markers to try group code up and figure out what was happening (it was a monstrosity with no formatting or comments lol)

But yeah day to day, even year to year nobody is printing off their code to look at it - let alone only 20 lines of it lol

It does work for code.. just not like this.