I know it won't be of much help - but I was looking for the exact same thing on linux; was just trying to view some log outputs that had bash ANSI color codes inside. Unfortunately, those ANSI color codes were spread across several lines - meaning 'cat'-ing the file and piping into 'less -R', 'most' and similar tools, would simply display the starting line where the color originated, but not the subsequent lines that should've been colored.
Funnily enough, I thought usual Linux tools like 'nano', 'gedit', 'vim' and whatnot would have capabilities for ANSI color codes in a text file, but it's very modest out there with info on ANSI color in text files in these editors. I've only found info on ANSI color for the test editor 'joe':
Cheap ANSI Color! - http://tldp.org/LDP/LG/issue01to08/articles.html#ansi
but couldn't get the recommendations there to work (also couldn't get 'emacs' to work either, at least not by directly reading a text file with ANSI color characters inside).
The good thing - it seems what you need, if you need ANSI color in text, is to look for ASCII art / NFO utilities as recommended above - and the one that I finally found, and was working for me, was tetradraw (via www.linux.org/apps/AppId_42.html ; can be sudo apt-get installed in Ubuntu ... actually, tetradraw is the name of the drawing/editor part - however there is a separate viewer that also works with ANSI color codes, tetraview).
Well, who would have thought, that you need to track down an ASCII art utility, in order to read log files :)
Anyways, hope this may somehow help in the further search of ANSI color text editors for Windows, too.. Cheers!