how to style list with nth-child()-CodePudding

I have the following

CodePudding user response：

You can think in groups of 4 :

The first and the last elements are red (4n 1 and 4n).
The second element is green (4n 2).
The third element is blue (4n 3).

.App {
  display: grid;
  grid-template-columns: 50% 50%;
}

.block {
  border: 1px solid black;
  height: 50px;
}

.block:nth-child(4n),
.block:nth-child(4n 1) {
  background-color: red;
}

.block:nth-child(4n 2) {
  background-color: green;
}

.block:nth-child(4n 3) {
  background-color: blue;
}

<div >
  <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>