That said, I do agree that the color coding is nice and adds to the efficiency and legibility of code, especially once your documents get a bit larger, and I definitely love how it looks (good ol' Monokai Bright, for me!), though I'd still advocate to hold off on getting into a fancier editor until you've gotten the basics down.
USE TEXTEDIT FOR HTML ON MAC CODE
In most programs, you can turn the auto complete functionality off, but it usually requires going into settings files and editing code that, certainly for beginners, could be an uncomfortable process.
You may not always have the luxury of using a fancier editor, so it's a great idea to use a basic editor (like TextEdit on your Mac, or NotePad on Windows) when you're just getting started to help you learn and remember the necessary components to the language(s) you're trying to learn. If you jump right into using an editor that has, say, a basic autocomplete feature when you're typing before you understand and remember what you would want to type anyway, you're doing yourself a disservice and potentially hindering your ability to learn, as you can rely on the crutch of the advanced editor to do the remembering for you.
As an aside, Jennifer listed some other great alternatives to TextEdit, but it's important to understand that it's not the editor you use that makes the code, it's you! The bells and whistles that other editors may offer can be great and save you a lot of time and headache, HOWEVER, it's best to only use those types of programs and features once you understand the basics.