Template:PosterGalleryCSS.css

/* Card frame */
.ksi-posters .gallerybox .thumb {
  border: 1px solid #777;
  background: #111;
  padding: 6px;
  box-shadow: 0 1px 4px rgba(0,0,0,.4);
}
.ksi-posters .thumb img { display:block; width:100%; height:auto; }

/* Caption container: make all non-link text white */
.mw-parser-output ul.gallery.ksi-posters li.gallerybox .gallerytext {
  color: #fff !important;
  font-size: 90%;
  padding-top: 4px;
  text-align: center;
}

/* Restore links to site’s normal colors (replace with your hex) */
.mw-parser-output ul.gallery.ksi-posters li.gallerybox .gallerytext a,
.mw-parser-output ul.gallery.ksi-posters li.gallerybox .gallerytext a:link {
  color: #f2a900 !important;           /* e.g., #f2a900 */
  text-decoration: underline;
}
.mw-parser-output ul.gallery.ksi-posters li.gallerybox .gallerytext a:visited {
  color: #f2a900 !important;           /* use your visited color if different */
}
.mw-parser-output ul.gallery.ksi-posters li.gallerybox .gallerytext a:hover,
.mw-parser-output ul.gallery.ksi-posters li.gallerybox .gallerytext a:focus {
  color: #f2a900 !important;           /* or your hover color */
  text-decoration: underline;
}