If you are just looking for an editor that will color code the code itself like Variables automatically become blue and HTML becomes red and if statements become green, then there is one that is free that you can download.
It is Text Pad, that is what I use.
It is very simple, and you can customize it to display the colors that you want.
Now if you are talking about something a bit more sophisticated, then you will have to turn to the expensive stuff. 🙁
here is the link to TEXT PAD-
http://www.textpad.com/