People who join later can create a small residence for their character outside a main city if they want to, not having to come up with a city and just being able to sit back and pick a location at will isn't such a terrible fate I should say
As for the outlines I'm talking about, here's the example:
Main City: Cape Havoc
Type: naval trade city with fortress
Location: the South-Western shore, more specifically in the middle between those two chokepoints where the sea is at its most narrow point.
Purpose: 1. Taxing any trade that comes through there. 2. Keeping enemies from sailing around the mountains to attack Loreos. 3. Shipping troops behind enemy armies
Economy: taxing nearby trade, own trade, fishing
Princess Loreainne's Home: Duskspire Palace
Type: Fortified Palace
Location: Central desert, in a straight line below the Large Town Trade Centre Hayden put there.
Purpose: 1. Home to the Princess and her warriors 2. Base of operations for them to keep control of the central desert, guard the trade routes and the chokepoint in between the two mountains.
Economy: supplied by the trade routes that pass close to it.
Type: small border village
Location: Northern border, close to the forests of Lenfal.
Purpose: Little. The Princess keeps some of her men here to keep an eye on the border and alert her of suspicious activity as well as apprehend any trespassers.
Economy: Farming. Often at odds with the forest inhabitants that live across the border when they use their woods for hunting / scavenging wood.
People would be free to use these outlines as they please and just use them to get inspired, but if they're not sure about something they could come to the city's 'governor' - in the case of these particular locations, me - who is only there to supply advice if asked.
As for colours... we already have our faction colours and overall building style guidelines, I think that's restrictive enough and will create enough of a unified look by itself. Remember few medieval cities were carefully planned out to the last brick either