Changing chart type & second axis on chart with 2-level axis labels

Example is attached.

I created a simple bar chart with 2-level axis labels. It is the number of aircraft per month; grouped by aircraft type.

I want to add a sixth group with the total. The total is a much higher number and due to scale it distorts interpretation of the other groups (i.e. the aircraft type).

So, I want to:

1. Add the total number of aircraft per month as an additional group
2. Plot these values on a secondary axis so as not to distort the scale
3. Consider changing the chart type to a line graph; just to see if it is visually more appealing

As a bonus question: Can one easily change the colors of the groups (i.e. the aircraft types)? All columns were blue when I created the chart and I have to select each column and change the color individually.

It's the first two-level chart I've made...pretty cool