I'm looking for this series I read years ago, probably on kindle 2015-2020. There is are two main countries. The northern one that has a russian/slavic feel, and their main color is blue. It is very cold and snowy, and rich people there have very big sleeves made with alot of fabric. the more facbric, the richer you are. The southern kingdom has an english/french feel, and it is where the heroine is from. Their main color is red.
The main character, the heroine, is blonde and the daughter of a duke or earl in the southern kingdom. I believe her father is dead, and she lives in the palace of the king. There are alot of nobles that live in this palace and it is important for political intrigue that you can navigate the palace and that you know what the location of your apartment means about your connection to the king. Guy 1 is the crown prince of the southern kingdom. There is a scene on a boat with him trying to court her. This is surprising to the heroine because she isn't in the best political position because of her dead father.
But our heroine decides not to marry guy one and instead runs away with guy 2. he was working at the southern palace, I think with horses, for a time, but he is really from the northern kingdom. our heroine runs away with him back to his small estate in the northern kingdom and they get married at the end of book one.
At the end of book one or the beginning of book two, guy 2 is assassinated. they are at the reception of their wedding and some men break in and kill him and try to kidnap the girl. it is later revealed that these men were sent by guy 1.
girl escapes kidnapers with guy 3. he was a good friend(?) of guy 2 and was at the wedding. he is also the second in line to the northern throne.
somehow the girl ends up back in the southern kingdom as the betrothed to guy 1, who is now the king. She learns that he was the one who had her husband killed and really tries to get away from him. He dies shortly before their wedding ceremony, but it is revealed that they were already legally married because guy 1 pulled some complicated strings to tie the girl to himself. this is important because now the heroine is queen. of a whole country even though she never really married the king.
she does her best as queen and really does quite well. She even finds a nice, kind, boring guy to marry. but she is really in love with guy 3, who is now the king of the northern country and is in a similar situation. he found a nice, kind, boring girl to marry. and they are convinced they can't be together because their nations are still rivals. but the nice, kind, boring sweethearts see them dancing together at a ball and are like "nope. you two obviously love each other, and we aren't going to get in your way. go get married." and they do and every works out between the countries.
somewhere in here, either in the first book or after the heroine returns to guy 1 there is a bit about the two countries trying to be friends, so they invite the current king of the northern country and his fiancée down to the southern country where guy one is king and heroine is his fiancé. and the two fiancés become friends and do a lot of work to make their countries friends and there is a scene where they switch colors, so our heroine wears blue and the other girl wears red.