<script src="https://kit.fontawesome.com/75227c97a9.js" crossorigin="anonymous"></script>

<div>
<i class="fab fa-envira fa-7x"></i>
</div>
div{
   text-align: center;
}

.fa-envira{
   animation: gradation 5s linear infinite alternate;
}

@keyframes gradation{
    0%{color:green;}
    50%{color:red;}
    100%{color:brown;}
}

External CSS

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External JavaScript

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