pfSense

Using pfSense-dark.css, the auto-complete pop-up currently does not specify a background image. This leads to theme.css applying a dark background image. Given the font color is also a dark color, this makes the text hard to read.

This can be fixed by setting background-image to none for ".ui-autocomplete". E.g.:
/** Styling for jQuery autocomplete widget */
.ui-autocomplete {
color: #212121;
background-color: #e0e0e0;
background-image: none;
}

See attached for example screenshots.