I would like to keep this as simple as possible a small mod or no mod at all if thats do-able. Heres the premise: I created a 18 player earth-scenario with the help of a creation scenario on rhys-earth map. I just have to have modern flags on the civilizations but I also want to change some of the colors as well like england to be red. I started changing some of the stuff in notepad but I am no guru and quickly had problems. Red england causes the flag to change colors and also caused problems when i changed japan to dark_red. so i downloaded some flags and added them into the bts flags then tried changing in the flags manually in notepad but this is not the way to do it i guess. I will go to any lengths to achieve this as this scenario has become an obsession of mine.
civs present : england,france,spain,germany,ottomanturks,russia,a rabia,egypt,ethiopia,
mali,zulu,india,persia,khmer,china,mongolia,japan, korea

I understand some of the civilizations are no longer present but possibly the present day country's flag like iran and possibly vietnam or thailand or whatever for the khmer.
The reason I want a small mod is my computer just goes too slow with these large mods that have present day flags. I play marathon games on this scenario in maybe 5 hours with no mods and I love it, but with a large mod it could take a few days. Any help would be awesome and I can even ship you a few $$ on a poker site for your help.

Check this: http://forums.civfanatics.com/showthread.php?t=315966. It's a tutorial about creating flags. It's not oriented on your specific problem, but it deals with how to create flags, specifying the teamcolours, mentions their influences on the flags and mentions the xml files you have to edit.