change background color CSS

I’m trying to change the background color of my featured slider on my site motelsmart.com

when using inspect element: if you right click the white area of the slider background and inspect element you should see the below css info.

element.style {
background-image: url(http://motelsmart.com/wp-content/uploads/2013/04/mechanical_services.png);
background-color: rgb(243, 22, 22);
display: none;
background-position: 50% 0%;
background-repeat: no-repeat no-repeat;
}

it gives you an option to change color “background color RGB” by clicking the little box and selecting a color. when I do this it changes the proper element and the background of the slider color will change. but I can not find the correct file, or css to actually to it permanantly. where is the proper file?????? how do i locate it?