<section>
    <p></p>
</section>
<section>
    <p></p>
</section>
<section>
    <p></p>
</section>
<section>
    <p></p>
</section>
<section>
    <p></p>
</section>
<section>
    <p></p>
</section>
<section>
    <p></p>
</section>

index.html

body, p, section {
    margin: 0;
}
section {
    background-color: blue;
    height: 50vh;
    display: flex;
    justify-content: center;
    align-items: center;
}
p {
    background-color: blue;
    padding: 10vw;
    border-radius: 100%;
}
section:nth-child(odd),
section:nth-child(even) p{
    background-color: yellow;
}

index.css