The Bartik theme allows setting the "Footer background" (color); however, there appears to be no way to set the text color. In the themes/bartik/css/style.css file, #footer-wrapper has:
color: #c0c0c0;
color: rgba(255,255,255,0.65);
replacing by "color: black;" immediately causes the text to show up. So it is not being overridden anywhere (or, at least, not successfully).