I also borrowed one of these programs, populating my comments to white as well. Finally, my curiosity overcame me, and I decided to check out how this little trick was done. Just before the comment, in the same line, was what appeared to be a blank, but upon further investigation, it was not a blank at all. It was a value of hex 22. I found this out by doing a display of the physical file member for my program source. When the source line is sent to the screen, using SEU, the hex 22 changes the display attribute of the remainder of the line to high intensity. Since I am using a 5250 emulator (Client Access), high intensity doesn't exist, so the emulator sets the color to white.
The following is a short RPG IV program that you can use to set your comments to appear in white, regardless of whether you prefer fixed-format or free-format calculations. You must use V5R1 (or later) to compile the program. I have called the program SRCCMTHI (for source comments high intensity):
This code will work if there are compile time arrays or tables, unless there is an asterisk (*) in position 7 followed by a space in 8 within the table/array data. If that happens, the space is turned into a hex 22. No results are guaranteed if you use this code, but it has worked well for me so far.
You may want to try the program first with a copy of your source program, just to see if you're going to like the results.