I have long suspected that green has a great advantage when it comes to districts and that yellow has a great disadvantage. I recently ran through the district deck and found out why I had this feeling. Green has way more districts than any other color, and yellow's cheapest district costs 3 gold! This doesn't make sense to me...

Does anybody know why this is the case?

Well, green is merchant districts, so it makes sense they would be plentiful and cheap. Lots of people hawking their wares in crude shacks down by the docks.

Gold is royal quarters, so again it makes sense they would be few and expensive - not everyone can afford to build such districts.

I suppose those are some legitimate flavor justifications, but that still leaves me confused as to whether or not there is design purpose, because as far as I can tell, it just makes the game less balanced.

I'm close to designing new districts for the empty color/cost slots and redistributing everything evenly, as I think this causes a serious imbalance as far as taxation ability goes. The last thing the Merchant needs is an easy way to get more gold. The first thing the King needs is a decent way to become more useful. A good thing for the game would be to make each color of district (besides purple) equally obtainable, such that the 5-color bonus isn't so impossible to get because you draw so many green districts and can't afford the yellow ones you draw.

Could public works be considered "noble," since they were most likely paid for by the government? Things like public fountains and gardens and promenades and stuff like that?

Oh and one more thing. Interestingly enough, blue doesn't have a 4-cost district. This seems really just wonky to me. Any plausible reason for that?

I'm close to designing new districts for the empty color/cost slots and redistributing everything evenly, as I think this causes a serious imbalance as far as taxation ability goes. The last thing the Merchant needs is an easy way to get more gold.

To each his own. I don't find anything particularly unbalanced about the distribution of districts, myself.

The Merchant is all about gold; that's what he does. He's not even the best gold generator, in my experience, due to the fact that he often gets Assassinated on principle. The Navigator is much better at creating a quick Gold infusion when you need it.

The first thing the King needs is a decent way to become more useful.

We prefer to play with the Emperor rather than the King. Makes the game more interesting.

A good thing for the game would be to make each color of district (besides purple) equally obtainable, such that the 5-color bonus isn't so impossible to get because you draw so many green districts and can't afford the yellow ones you draw.

You are aware that you don't have to build everything you draw, right? There's no hand limit, so you can just hold on to cards you don't care about building. This also provides you insulation against the Wizard and gives you some cheap cards to throw at the Emperor in "gratitude" when he crowns you.

In our games, people almost always get the 5-colour bonus by the end of the game.

Could public works be considered "noble," since they were most likely paid for by the government? Things like public fountains and gardens and promenades and stuff like that?

The idea of public works being Noble districts is a fine idea, although to be honest I don't know how often that sort of thing happened in the middle ages. It's a fantasy world, though, so it's not like we need to adhere strictly to "realistic" expectations.

Oh and one more thing. Interestingly enough, blue doesn't have a 4-cost district. This seems really just wonky to me. Any plausible reason for that?

It's an interesting observation, but I doubt it has any serious implications. Go ahead and make a 4-cost Blue district if you want to.

The seeming imbalance in the colour rarity and cost is very much an intentional part of citadels. It fits both the theme and the gameplay, making the merchant a very fast way to accumulate gold, which is what the merchant is meant to do.. Blue and red are identical as far as quantity (11 districts, 4 unique types) and cost go, while yellow has 12 but only 3 unique districts, combined with a high gold cost, in order to balance the power of gaining the crown. The fact that the non-green colours are fare less common prevents the merchant from losing his job as the main money maker, and balances out the power of the other abilities.

The distribution of districts is not a design error, but a well tested gameplay tool. I now appreciate the consideration that was put into citadels, even on a level that is at first not noticeable.

I do like the idea of adding your own districts, particularly purples, and i think that this could be a fun game mechanic experiment, if i could find a group willing to test it.