get all the input value and make an addition

Answer 1

Try this:

var $inputs = $('.liste_couleur_qty li input');
$inputs.keyup(function() {
   var result = 0;
   $inputs.each(function(){
     result += parseInt(this.value, 10);
   });
   $('#qtyvalue').html(result);    
});

This would need to be in a document ready handler or in a script block after the elements in question (many people put their scripts at the end of the body).

In your code, input.onkeyup = ... wouldn't work because there is no variable input (it doesn't automatically pick up all input elements), and also using someElement.onkeyup = only lets you attach a handler to one element at a time. Use jQuery to bind the keyup handler instead. Also, to use the total at the end just use result, using result.value wouldn't work.