.flag {
width: 300px;
height: 200px;
border: 1px solid black;
position: relative;
}
.red {
backgroundcolor: red;
width: 100%;
height: 33.33%;
}
.white {
backgroundcolor: white;
width: 100%;
height: 33.33%;
}
.blue {
backgroundcolor: blue;
width: 30%;
height: 33.33%;
position: absolute;
right: 0;
}