Change classes on click

toogle classes between buttons

HTML
<button class="btn clr2">1</button>
<button class="btn clr2">2</button>
<button class="btn clr2">3</button>
<button class="btn clr2">4</button>
<button class="btn clr2">5</button>
<button class="btn clr2">6</button>

CSS
.clr{
    color : red;
}
.clr2{
    color : blue;
}

JS
$('.btn').on('click',function(){
  $('.btn').removeClass('clr').addClass('clr2');
  $(this).removeClass('clr2').addClass('clr');
})