.flex-container{
    width: 300px;
    height: 200px;
    background-color: #c4c4c4;
    border: 1px solid black;
}
.flex-item{
    color: white;
    background-color: #ff5252;
}
.flex-item:nth-child(2n){
    background-color: #bf5e5e;
}