1- If you want to style ALL widget title doing with rules like below in Main Options > Sidebar & Layout > Individual widgets > Widget title BG CSS+ box
{border-bottom:2px solid white;margin-bottom:10px;}
and use the widget title text color box for the color.
If you want to style the widget titles only in the footer widget area, you can add a slightly different rule in Main Options > Fonts & Custom > Custom CSS Rule box
#colophon .widget-title {border-bottom:2px solid white;margin-bottom:10px;}
You may need to add !important on some of the properties.
2- If you need to change the post title everywhere use the post specific page options.
If you need to change the post title color in the footer, given it is a link, you need to use the rule below in Main Options > Fonts & Custom > Custom CSS Rule box
#colophon .post-title a {color:white;}
You may need important
#colophon .post-title a {color:white !important;}