CSS: How to specify a child div

Example:

.grid-container > div {
  background-color: rgba(255, 128, 255, 0.8);
  text-align: center;
  padding: 20px 0;
  font-size: 30px;
}

References:

https://www.w3schools.com/cssref/tryit.asp?filename=trycss_grid-template-columns2