NFT preview card component mobile first

Hello everyone 👋

I actually have a question for this challenge. The challenge includes the use of a hr in the HTML that has a specific color and the method that I use in CSS works for the main browser that I use (firefox) but when I see the page with other browsers (brave and safari in my case) then the color of the hr returns to the default one. Does anyone knows how to solve this issue?

Thanks for the Help