Colour-coding is definitely a matter of style. Personally, I very much like simple colour-coding. I find that even just colouring strings, numbers and comments makes code so much more readable. But maybe I'm not writing good code :)

Apart from the subject matter, I find it interesting how you phrase your argument. Inferring that code will look like a christmas tree if you use the ever-slightest colour-coding definitely is an unusual chain of reasoning... Good arguments don't need strange reasons to support them.