Template:PeriodicTableGrid/styles.css

.wikitable.periodic-table {
  background: #05070a;
  color: #eee;
  border: 1px solid #333;
}

.wikitable.periodic-table th {
  background: #111824;
  color: #e0f4ff;
}

.wikitable.periodic-table td {
  width: 3.2em;
  height: 3em;
  padding: 0.2em;
  border: 1px solid #222;
}

.wikitable.periodic-table td a {
  color: #fff;
  text-decoration: none;
}

.wikitable.periodic-table td a:hover {
  text-decoration: underline;
}

/* Categories */
.pt-alkali         { background:#4b1f1f; }
.pt-alkaline       { background:#4b2c1f; }
.pt-transition     { background:#23414d; }
.pt-posttransition { background:#3c3c4d; }
.pt-metalloid      { background:#355032; }
.pt-nonmetal       { background:#253a57; }
.pt-halogen        { background:#5a2e5a; }
.pt-noblegas       { background:#2b3f5f; }
.pt-lanthanide     { background:#4c284d; }
.pt-actinide       { background:#4c2236; }
.pt-lanthact       { background:#222; font-style:italic; }