Change blog category colour on home page


I’d like to recolour the blog category on my home page. I’ve used a code posted in response to a similar query which worked when I was in Tablet mode, but it reverts back to the default blue when in full screen mode.

This was the CSS code I used:

    .elementor-widget.elementor-widget-athemes-blog .post-content {
       background-color: #131315 !important;  

It seems to have corrected itself overnight, the CSS code is now working.