Do we have any straight manhwa s where the female lead has hurly brown hair, and the male ...

This one's pretty good! Mc has curly brown hair ^^
https://www.mangago.zone/read-manga/is_it_a_fortune_or_is_it_a_woe/

https://www.mangago.zone/read-manga/the_reason_why_raeliana_ended_up_at_the_duke_s_mansion/

https://www.mangago.zone/read-manga/under_the_oak_tree/

here FL has red hair, and the ML has straight black hair
http://mangago.zone/read-manga/priscilla_s_marriage_request/

and here you can try and find more
https://www.mangaupdates.com/series?category=Brown-Haired+Female+Lead_Black-Haired+Male+Lead&perpage=50&orderby=rating