Settlement buildings should be enough to get you through day 4 without decos at least. On day 5, my camp-world is still yet to build a barracks and has been fighting red nodes with this:
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I only really started working polynesia recently, so it's still missing - I have some of the GBG building, but I can't maintain it constantly so I seem to never place it instead lol.
It's getting tight there on 5, I'll probably have to build some extra units and boost soon. But I've had a good amount of time to increase my coin and supply production before building decos. Both it and my main's settlement are roughly like this:
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21 units of coin production and 16 units of supply production (where 1 unit is the production of a rooftile or butcher). My main got there a little sooner because it's built harvest hubs while they don't fit with my camp-world's objective. So it might get one more deco when it's "time". I'm currently saving for my big deco drop when i need it.
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I think the "pattern" you're observing with where red and blue come from in events is just a result of small samples. Blue was prominent in fellowship. Red is more prominent in Halloween and Winter (possibly because they now made red more important for this version of the maps).