[Chartjs]-Chart.js tooltips callback function with pie charts

Try this:

tooltips: {
    mode: 'label',
    callbacks: {
        label: function(tooltipItem, data) { 
            var indice = tooltipItem.index;                 
            return  data.labels[indice] +': '+data.datasets[0].data[indice] + '';
        }
    }
},