1) You can change those colors for the box content using this in Theme Options => Custom CSS
/* Hover */
.spb_box_content .box-link:hover {
opacity: .1;
background-color: rebeccapurple;
}
/* Active */
.spb_box_content .box-link:active {
opacity: .1;
background-color: red;
}
/* Visited */
.spb_box_content .box-link:visited {
opacity: .1;
background-color: blue;
}
2) This is the default mobile layout, on small screens the layout is stacked vertically.
3) You need to enabled the Page Builder for the Portfolio. Add “portfolio” here: Page Builder => Page Builder Post Types Pages Posts Team