I understood the problem, but I found the page's explanation a little confusing at first. In particular, "lexical differential highlighting" misled me, because

I understood the problem, but I found the page's explanation a little confusing at first. In particular, "lexical differential highlighting" misled me, because the word "differential" made me think that his algorithm was comparing lines or tokens in some way, and it doesn't do that. Basically, this algorithm tokenizes the source code, and tries to color each token so that identical tokens have the same color, but similar-looking tokens have very different colors. When tokenizing it specially handles comments and quoted text. That's an interesting approach to countering errors from "it's almost the same but I didn't notice they were different". I wonder - if I were trying to review source code that were malicious, maybe I could vary the color algorithm using a random source so that the source code writer couldn't make different tokens look similar in color. That might be an interesting countermeasure to some kinds of underhanded code.