Swift 5.62 Child theme> not WPMU Dev

This is about the swift 5.62 theme. (Not a WPMU Dev) I know i can change the color in the swift design options tab, but i want to change it in the code so every site i activate it on will not have to be changed. In the design options tab its called “Navigation border” but i cannot find it in the style.css Its the two lines above and below the title. alclassifieds.mtb1701.com/