I am trying to color the 2nd (Appointments) bar based on the ratio (Appointments/Target) However, it does not seem possible via the Color under Chart Properties - Is there any other way?
Unfortunately, color rules are pretty limited and you won't be able to do what you want to do. I would suggest looking at the bullet chart for this. It will put a small line at your target value and will make it easy to see when your appointments are above or below the target line.