I really hope Avast 7 allows you to switch between Avast own skin and Windows defaut Aero skin 
Please add this option!
I rather doubt that is going to happen as there is no skin as such.
When you consider that the beta for version 7 is likely to be around the end of this month beginning of next month, so it isn’t likely new features/function, etc. will be added and nothing has been mentioned about any interface changes like this.
I believe there are contrast changes/improvements available for the visually impaired, but I don’t know how they are going to achieve that and if that would mean there might be a way to change the interface in a way other than contrast.