Scheduling app

I'm looking for an app that will allow me to schedule people in a visual way. I need to use it for an event where a group of 10-15 people will have a variety of different tasks to do over a period of about 6 hours. I need it for my own planning purposes (so I can visually organize those people and tasks, and easily move things around as I need to make changes or see timing conflicts), as well as to provide a time guide for the participants.

What I'm looking for is an app that will allow me to:

• assign names different colours
• organize people on a timeline so that I can enter a time period (eg 1pm-1:35), displayed graph style
• enter descriptions for the different times

I've tried Swifty, which is close, but it has a limitation whereby time slots that are close together (one "shift" ending at 11 and the next beginning at 11:15) overlap, and there's no way to stretch out the view, if that makes sense.

The only other option I can think of would be to use Numbers, but I haven't seen any templates that look like what I'm envisioning.

Thanks