How can I change image gallery/boxes/border color to black?

I’m using Uncode. It offers only 2 options for the border of boxes in an isotope image gallery: White and grey. I do not want either. I want it to be solid black. How do I change this?
Thank you!


In you don’t have options to choose solid black border then you can do it by overwriting the css. as like: border: 1px solid #000 !important;