gistfile1.js

'use strict';

var inputs = document.querySelector('input[type="checkbox"]'),
    camiseta = document.querySelector('#camiseta'),
    i = 0,
    len = inputs.length,
    input;

for ( ; i < len; i++) {
    input = inputs[i];

    input.addEventListener('change', function(){
        camiseta.style.backgroundColor = this.value;
    });
}