The following lines of code when added to the theme.css file within the theme at the end solve the problem and make it look to my eye in line with the rest of the theme.
#cboxOverlay {
background: #000;
opacity: 0.9;
filter: alpha(opacity = 90);
position: fixed;
width: 100%;
height: 100%;
}
#cboxContent a.icon-ato-cancel.close-edit:hover {
color: #fff;
}
#cboxContent a.icon-ato-cancel.close-edit {
color: #ccc;
font-size: 0.8em;
font-family: Arial,Helvetica,sans-serif;
}
#cboxContent .ui-submit .ui-btn-hidden {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
-webkit-appearance: none;
cursor: pointer;
background: #fff;
background: rgba(255,255,255,0);
filter: Alpha(Opacity=0);
opacity: .1;
font-size: 1px;
border: none;
text-indent: -9999px;
}