<h1 id="colorchange">ESTAMOS FAZENDO TESTE DE CORES COM JAVASCRIPT!</h1>
<input type="text" name="Cor" id="whatcolor"><br /><br>
<button type="button" onclick="newcolor('whatcolor')">Mudar</button>
<script>
        function newcolor(thecolor) {
        document.getElementById('colorchange').style.color = thecolor;
    }
</script>