So you're bored of the same old blue for the Scipii and you think Gaul should get another colour. Well, here's where you can change that.
(Note: This does not change every colour for everything for the faction, just the region colours and strat flag)
First, we need to know what file we're going to change.
Go to Rome - Total War\data.
There, if you scroll down (or search) you will see a file called descr_sm_factions.txt. Open it.
You will see this:
faction romans_julii
culture roman
symbol models_strat/symbol_julii.CAS
rebel_symbol models_strat/symbol_slaves.CAS
primary_colour red 165, green 20, blue 20
secondary_colour red 0, green 0, blue 0
loading_logo loading_screen/symbols/symbol128_julii.tga
standard_index 0
logo_index 23
small_logo_index 248
triumph_value 5
intro_movie fmv/intros/julii_intro_final.wmv
victory_movie fmv/victory/julii_outro_320x240.wmv
defeat_movie fmv/lose/julii_eliminated.wmv
death_movie fmv/death/death_julii_grass_320x240.wmv
custom_battle_availability yes
can_sap yes
prefers_naval_invasions no
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;There's a lot of stuff there we're not going to mess around with. Specifically, we're only going to change the primary_colour & secondary_colour.
Now open Paint, and go to the tab at the top that says Colours. Click Edit Colours. Then, click Define Custom Colours>> on the window that appears.
You will see this:
(http://img221.imageshack.us/img221/1566/dsmftutorial01.png)
Info
RTW uses RGB for the faction colours. The RGB of black is 0, 0, 0, but red is 255, 0, 0, green is 0, 255, 0 etc.
In a region on the mini-map, there is a big colour filling nearly all of the region and then a border.
primary_colour = the main region filling
secondary_colour = the border
When you change the primary colour, the region colour changes, but the banners of campaign figures changes as well.
On Paint, select the colour you want, look at the RGB value, and change the RGB values in descr_sm_factions.txt. It's that simple.