body, html {
    margin: 0;
    padding: 10px;
    justify-content: center;
    text-align: center;
    align-items: center;
    height: 100%;
    animation: colorChange 15s infinite alternate;
    display: block;
}

header {
    font-size: 4rem;
    font-family: Arial, Helvetica, sans-serif;
}
h1 {
    font-size: 3rem;
    font-family: 'Times New Roman', Times, serif;
    font-weight: bold;
    color: black;
}

p {
    font-size: 1rem;
    line-height: 1.6;
    color: aliceblue;
    font-family: Arial, Helvetica, sans-serif;
}

.your-element {
  border: 50px;
  animation: colorChange 5s infinite alternate;
}

@keyframes colorChange{
    0% { background-color: red;}
    25% { background-color: yellow;}
    50% { background-color: green;}
    75% { background-color: blue}
    100% { background-color: red;}
}