ListXP might work for you; dunno how it will handle the color codes, but I use it daily. It's tiny, fast,and handles files of essentially unlimited size. The link is to a review; you may have to ...
Windows only: If you frequently open NFO files—those pesky little text files that often contain scrambled ANSI art—NFOPad is a small Windows Notepad clone designed to display them properly. NFOPad ...