Thank you Emziie! This helps. Remaining questions:
Is there also a bonus for the specific players who helped to flip the city
(meaning, is there a prestige increase in the actual city that was flipped or other bonus, or does it not matter at all if a player helped to flip the city or did nothing)?
And does the bonus stay (blue city remaining red) in following days or is it only 1x?
And if blue takes it back the following day and then red takes it again the day after that....
do both fractions keep getting the bonus every day at reset?
No, there is no specific bonus for the players who helped to flip it. Everyone on the side that flipped it will receive the same bonus.
If blue takes it back the next day - they get the bonus at the daily reset where it flips, if red take it back the next day then they get the bonus at the reset.
If the City flips to red at the reset, and remains red at the next reset then no-one receives a bonus as it has to change color to receive a bonus.