lucaluca said:I wrote this suggestion in another thread, but I'm going to add it here since is official: my suggestion is fro the CoA of the county of Byzantion, it was historically...a crescent moon with a star! (yes the same of Turkey today).
Here a quote from the original thread:
About CoA of Constantinople (or Byzantion as it's called in the game), I read many times that the original flag of the city was what is actually the flag of Turkey, or something similar: the original simbol was an crescent moon, and Costantine (or some ather emperor) added the star which symbolize venus or Diana for pagans and the Vergin mary for Christians. When the Ottomans conquered the city, they used that flag as the flag of the empire; here the proof, only one link but I found severals (italian also):
http://www.crwflags.com/fotw/flags/tr.html
here a quote:
Many traditions explain the star and crescent symbol. It is known that Diana was the patron goddess of Byzantium and that her symbol was a moon. In 330, the Emperor Constantine rededicated the city - which he called Constantinople - to the Virgin Mary, whose star symbol was superimposed over the crescent. In 1453 Constantinople was captured by the Ottoman Turks and renamed Istanbul, but its new rulers may have adopted the existing emblem for their own use"
Other several links:
http://islam.about.com/library/weekly/aa060401a.htm?terms=crescent
http://www.symbols.com/encyclopedia/24/2464.html
http://www.islamonline.net/fatwa/english/FatwaDisplay.asp?hFatwaID=49011
very important this upper, is a fatwa!!!![]()
http://archnet.org/forum/view.tcl?message_id=40355
http://dictionary.reference.com/search?q=crescent
this is a dictionaryhere a quote:
crescent
\Cres"cent\ (kr[e^]s"sent), n. [OE. cressent, cressaunt, crescent (in sense 1), OF. creissant increasing, F. croissant, p. pr. of cro[^i]tre, OF. creistre, fr. L. crescere to increase, v. incho.; akin to creare to create. See Create, and cf. Accrue, Increase, Crescendo.] 1. The increasing moon; the moon in her first quarter, or when defined by a concave and a convex edge; also, applied improperly to the old or decreasing moon in a like state.
2. Anything having the shape of a crescent or new moon.
3. A representation of the increasing moon, often used as an emblem or badge; as: (a) A symbol of Artemis, or Diana. (b) The ancient symbol of Byzantium or Constantinople. Hence: (c) The emblem of the Turkish Empire, adopted after the taking of Constantinople.
and many more links...
About colors, no one says...; I can imagine a flag like the image in the first link (moon and star yellow on white), or moon and star yellow over blue (imperial colour), or moon and star yellow over purple (imperial colour and colour of the city at twilight, when the moon and the planet venus appear togheter).
Actually the flag of the Ottomans looked like this after taking Constantinople, the star was added in the 1780's.
The present Türkey flag only dates back to 1844.

Ottoman flag after taking Constantinople.
NOTE: Flags and research made by MKJ with some help from Tuna if I'm correct.
Link to MKJ's turkish flags: http://jgdahl.tripod.com/turkish.html
Link to thread over in the EU2 forum: http://forum.paradoxplaza.com/forum/showthread.php?t=37341&page=93&pp=25