When I wrote App::perlhl a few weeks ago, I was mostly concerned with getting it working. I picked colours more-or-less at random, and I noted that I planned to tweak them to achieve better readability. I'd like to do some hallway usability testing - if you're interested, please try cloning my git repository and playing with the branches. Master has one colour scheme, and I created colour-2 and colour-3 to test two more schemes. Try them out & let me know what you find most easiest to read. If you want to play with the colouring yourself, I'd be happy to accept whichever one people find best. Thanks!