function get(format) {
		var ret;

		if (stops) {
			ret = merge(input);
			ret.stops = [].concat(ret.stops);
			each(stops, function (stop, i) {
				ret.stops[i] = [ret.stops[i][0], stop.get(format)];
			});

		// it's NaN if gradient colors on a column chart
		} else if (rgba && !isNaN(rgba[0])) {
			if (format === 'rgb') {
				ret = 'rgb(' + rgba[0] + ',' + rgba[1] + ',' + rgba[2] + ')';
			} else if (format === 'a') {
				ret = rgba[3];
			} else {
				ret = 'rgba(' + rgba.join(',') + ')';
			}
		} else {
			ret = input;
		}
		return ret;
	}
Return the color a specified format
@param {String} format