Meteor.js onRendered not triggered for dynamic template on data change

I'm trying to integrate a dynamic template called "page-event" on "page-main" which depends on data from a helper:

HTML MAIN

{{>Template.dynamic template="page-event" data=selectedEvent}}

JS MAIN

Template["page-main"].helpers({
    selectedEvent: function() {
        var eventId = Template.instance().selectedEventId.get()
        event = Collections.Events.findOne(eventId);
        return { event: event };
    }
});

JS EVENT

Template["page-event"].onRendered(function() {
        const ti = this;
        var eventData = this.data.event;
        console.log("RENDERING EVENT");
        // Color picker
        var colorPicker = $(ti.find(".colorSelect"));
        colorPicker.colorpicker({ format: "hex" });
        colorPicker.colorpicker("setValue", eventData.color);
        colorPicker.colorpicker().on("hidePicker.colorpicker", function(event) {
            var rgb = event.color.toRGB();
            Meteor.call("setEventVsColor", eventData._id, "rgb(" + rgb.r.toString() + "," + rgb.g.toString() + "," + rgb.b.toString() + ")");
        });
});

JS EVENT (incl. Jankapunkt's solution)

    Template["page-event"].onRendered(function() {
            const ti = this;
            const data = Template.currentData()
            var eventData = data.event;
            ti.autorun( function() {
              console.log("RENDERING EVENT");
              // Color picker
              var colorPicker = $(ti.find(".colorSelect"));
              colorPicker.colorpicker({ format: "hex" });
              colorPicker.colorpicker("setValue", eventData.color);
              colorPicker.colorpicker().on("hidePicker.colorpicker", function(event) {
                var rgb = event.color.toRGB();
                Meteor.call("setEventVsColor", eventData._id, "rgb(" + rgb.r.toString() + "," + rgb.g.toString() + "," + rgb.b.toString() + ")");
            });
        });
    });

Whenever the data retrieved by the helper is modified, I expect the template to re-render, since some of the onRendered functionality (excluded in this example) depends on the new data. But onRendered never triggers. What am I doing wrong?

Edit: After using Jankapunkt's solution, some of the onRendered components trigger for every one of the parent template's collection items, not just the item passed to the child template.

You can check for reactive data updates using Template.currentData() within an autorun (Tracker) computation:

Template["page-event"].onRendered(function() {
  const instance = this
  instance.autorun(() => {
    const data = Template.currentData() // reactive data source
    // ... process data
  })
});

According to the BlazeJS documentation it should work for onCreated, as well as onRendered