I've done a lot of experiments. Most turned out wonderful ways to ruin readability. (I combine those to highlight a single line of code in an article to troll the reader)

It is a huge problem that we are so used to what we have. I can barely make sense of the examples in the article.

I think it calls for actual research where we collectively catalog the approaches, experiment (on humans) and attempt to have conclusions about them.

What surprised me most in the experiments is that giving each different variable and each function call a different color makes scanning over the code much easier.(function declaration and call the same color)

Also a very successful experiment was to color the opening and closing brackets the same color and use a different one for each level of nesting.

One that I failed to code/design properly but looked very promising was to faintly color the background of each level of nesting so that the color gets more visible the deeper you go. It makes the hot spots jump out.

Probably the funniest was to have basic html tags in comments (like headings, pictures and videos) then define a css at the top of the code.

   /*<style>
   body {background:Medium Blue;color:white}
   comments {color:lime}
   var {color:olive}
   h1 {font-family:inferno}
   </style>*/