in html onclick change colour code example

Example 1: onclick change text color javascript

<script>

    document.getElementById('change').onclick = changeColor;   

    function changeColor() {
        document.body.style.color = "purple";
        return false;
    }   

</script>

Example 2: css onclick change color

<style>
.dabutton:focus {
    background-color:yellow;
}
</style>
<button class="dabutton"></button> // <-- usage