Вячеслав

.pink_link
{
    color: pink;
}

<a class="pink_link" style="color:pink;">My pretty link</a>

function category_change()
{
    var url = $(this).val();
    window.location.href = url;
}
$('#category-select').on('change',category_change);

var select = document.getElementById('category-select');
select.onchange = function()
{
    window.location.href=this.value;
}