My boss told me there was a study that found that green on black was the easiest to read and the best on the eyes for long periods of looking at a screen. Unfortunately I don't have a link to the study. I use TextPad, myself, black on white, with syntax highlighting: functions in blue, strings in green, comments in orange, brackets in red, and the like. I'm still learning Perl and it's easier when I can quickly tell the difference between each part of the code. Plus it helps find simple errors; if you forget a closing " or ', the whole rest of the file turns green :-)