<div class="wrapper">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
  <div>10</div>
  <div>11</div>
  <div>12</div>
</div>

.wrapper > div {
  background-color: orange;
  border: 1px black solid;
}

.wrapper > div:nth-child(odd) {
  background-color: indianred;
}

.wrapper {
  display: grid;
  grid-template-columns: repeat(12, 1fr)
}