I was just browsing flag colors and was curious if there was any correllation between colors in flags, and noticed a (very surface level, admittedly) correlation, that more wealthy countries typically had blue in their flags (Sweden, Finland, US, UK, Australia, albeit North Korea, Venezuela, and Chad) and was curious if there was a common agreement towards what colors go into flags or maybe better stated, if alliances between countries is brought into consideration with flag designs?

I'd like to apologize if this is a very naive question, but I'd appreciate if this could possibly start as a general discussion of flag design or if that's a topic that has a subreddit, I'd love to hear where to go.

Thanks!