It reduces productivity and adds headache.
Code is not a textbook. A good programmer has to always look at different pieces of code and would lose himself in the mess of symbols if there is no indents and block highlights..
And if he's meaning to compare it to prose, while they typically lack color (due more to the means of printing than the format, check out old manuscripts and they use color quite often), they use punctuation and other methods of emphasis like bold, italics, size, and underlining.