Both type of events start to affect the game from the beginning of each round. The brown events are effects that are insta-resolved and the blue events may affect the game for the whole round (turn) and/or up to the end of the running chapter.
So, if a blue event affects any of the actions you would like to play, the rules just reminds you to keep this in mind.
I hope this helped
Maybe I'm reading the rules wrong, but is this right?
Blue events - Take place right before playing my card for the turn. After receiving the beneficts from the event played and from moving the favor mark.
Brown events - Take place before receiving the beneficts from the event played and from moving the favor mark.