Custom bindings to use Chart.js with Knockout.js

ko-chart.js

/*global ko, Chart */

(function(ko, Chart) {

	ko.bindingHandlers.chartType = {
		init: function(element, valueAccessor, allBindings, viewModel, bindingContext) {
			if (!allBindings.has('chartData')) {
				throw Error('chartType must be used in conjunction with chartData and (optionally) chartOptions');
			}
		},
		update: function (element, valueAccessor, allBindings, viewModel, bindingContext) {
			var ctx = element.getContext('2d'),
				type = ko.unwrap(valueAccessor()),
				data = ko.unwrap(allBindings.get('chartData')),
				options = ko.unwrap(allBindings.get('chartOptions')) || {};
			
			if (this.chart) {
				this.chart.destroy();
				delete this.chart;
			}
			
			this.chart = new Chart(ctx)[type](data, options);
		}
	};

	ko.bindingHandlers.chartData = {
		init: function(element, valueAccessor, allBindings, viewModel, bindingContext) {
			if (!allBindings.has('chartType')) {
				throw Error('chartData must be used in conjunction with chartType and (optionally) chartOptions');
			}
		}
	};

	ko.bindingHandlers.chartOptions = {
		init: function(element, valueAccessor, allBindings, viewModel, bindingContext) {
			if (!allBindings.has('chartData') || !allBindings.has('chartType')) {
				throw Error('chartOptions must be used in conjunction with chartType and chartData');
			}
		}
	};

})(ko, Chart);

Any option of using the same without defining the colours inside the datasets? I am intending to fetch data from back end services. So Defining colours at that level is a bit tricky because I won't have any idea about the dataset's size.