Hello Blush – I changed the Welcome section background to black and my images have a highlight around them

Is this for Kadence?  If so, when in the page editor, click on the image, then over on the right in the editor scroll down to the tab that says image shadow, and turn that off.  
 
If this is for Genesis, it is coded in to the CSS, you can add this to your additional CSS in the customizer.
 
.home-one .widget:nth-child(2),
.home-grid .featured-content .entry,
.home-grid-2 .featured-content .entry,
.home-two .widget:nth-child(1) {
box-shadow: none!important;
}