The person who told me I used it offensively didnt really explain why to me. I've avoided saying the word for years straight now. I still don't know how to say the word ethnic appropriately.
I can't help but think I might have said it with a colonial perspective
Btw, why is it perfectly fine here?
I think you chose a bad example for this - afaik cornrows are specifically an African American thing, which would make them an ethnic hairstyle - a hairstyle specific to people of African American ethnicity. I know that your point was using it as a replacement for black is offensive, but the specific example ended up making a sentence that has its own valid meaning.