We're really good at parsing code, thanks to languages designed to be easy to read and to our style guides (unless we don't have one, of course). Highlighting keywords is uselessly tiring for the eyes IMO.

What matters most is to separate code from what's not code and which doesn't follow the same rules: comments and string-like literals.

In my vim color scheme (https://github.com/Canop/patine) I only have three colors: one for code, one for comments, one for strings, and I find reading the code easier and less tiring this way.