Hey guys,
I did some experimentation with the Mod Tools and after some fiddling I managed to change Sera's hair color to black.
Technically this mod gives Sera the same hair color as Cassandra.

No texture change, just modifications on the Mesh Materials, so no other character's appearances' should be influenced.
I am actually not sure if anyone has done this before.
This is quite experimental as far as I am concerned, so if you find issues, please let me know.

Should be compatible with any mod that doesn't change Sera's hair mesh.

Installation:
Please follow the instructions on the page of the Mod Manager

Known Problems:
Well, her eye brows are still blonde, if that bothers you. I might make an optional download with a modified face texture if someone wants it.

Credits:
Bioware/EA for the game, Ehamloptiran for the Tools, esCanor for the tutorial I used.

Regards,
    Toloc