If you google "Jeff Cooper's Commentaries" it will bring up several sites that have .pdf archives of several years of his his commentaries. This was sort of the original "blog". He didn't publish them online himself, if I understand correctly, but wrote a monthly newsletter of sorts that he sent out to friends, peers, former students who had gone through the original gunsite academy under his tutelage, etc.
A few bits of the monthly newsletter then were cut and edited down to be included as the last page article, also titled Jeff Cooper's Commentaries, in Guns and Ammo magazine. The full newsletter was much better.
Anyway, once you download the .pdfs it will be a simple enough task to search for the phrase "color code". He referenced the code often and I believe I recall articles where he discussed its origins. In latter years he sometimes complained that others had added things that were not part of his code such as a "condition black". I also recall a commentary after 9/11 when he was amused that the federal government had adopted a similar color for the national threat level.
I also have some of his books but don't recall the code mentioned there. The commentaries are probably your best bet.
Cooper was a great man. Well-read, well-educated, well-traveled, intelligent and eloquent. I looked forward to his commentaries every month. Even the style of his prose was refreshing and stimulating. Thinking about him now makes me realize how sad I still am that he's no longer with us.
