story identification - Looking for a book series about a girl and her friends captured and sold as slaves

I'm trying to find the name of a book series I read about 10 years ago. It might be a children/young-adult series since I was fairly young. There is also a small chance it was written by a french author, as I read it in french. The series is composed of at least three books, maybe more. Here is what I remember :

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  The main character is a poor girl/young woman, but there are several point of view characters

  
  


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  At the beginning of the first book the plot is set in a city where rich people live in the city center and the further you go from the center the poorest people are. Moreover, the houses are painted according to the wealth of the owner. It was something like : the richer had red houses, the poorer blue houses, and the moderately wealthy purple (it was not those colors in particular but it was something like that)

  
  


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  At the end of one of the book there is some kind of uprising and the people paint all the houses in multiple colorful shades (to symbolize the new found equality between the citizen)

  
  



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  At some point the main character and other peoples of the city get captured (maybe after some kind of war the city was involved in), separated and sold to slavery

  
  


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  One of them, an older boy, become a soldier and learn a special fighting technique that looks like dancing (and he grows to like it)

  
  


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  Another of the captives, a young girl (the sister of the main character if I recall correctly) get marked with a fire-heated mark to show her condition of slave

  
  

That is all I remember, I have no clue about the time or geographic setting nor the story details.

I know it's not much to go by, any help would be greatly appreciated, as I would like to find these books and read them again.

Answer

Could you be thinking of the Wind on Fire series by William Nicholson? There are three books, The Wind Singer, Slaves of the Mastery & Firesong, and they are centered around the lives of brother and sister Kestrel and Bowman Hath. I read them as a kid too!