Threads of Destiny: Loretta and the Magic Mechanic

In a closed kingdom where technology and magic, brought by a guide from another world, merge, only those with magical powers belong to the privileged class, and the threads spun with their magic serve as the power source. Royalty and nobility have hair colors that symbolize the magical attributes of wind, water, fire, and electricity, while commoners without magical powers are born with brown or black hair. In this world of magical privilege, Loretta, a countess's daughter, is born as an illegitimate child with black hair, a symbol of the common people. Raised in secrecy, the unfortunate Loretta faces a new destiny—!!

(Source: Earth Star Entertainment, translated)