Hi, welcome to the forum!
During the national anthem is it proper to have a vehicle moving that is decorated in red white and blue? What would make it proper if anything?
The Flag Code does not address this issue. However, the usual protocol in the military is that all vehicles are stopped during the playing of the national anthem. US Army Regulation 600-25 says:
"When ceremonies (excluding military funerals) are being conducted, moving vehicles will be brought to a halt. Military passengers and drivers will dismount and render the appropriate courtesy. When riding in buses and trucks, only the senior occupant will dismount and render appropriate courtesy."
The Air Force (AFMAN 36-2203) is slightly more specific:
"In vehicles during an Air Force flag ceremony, the driver brings the moving vehicle to a stop at the first note of the national anthem or To the Colors. Personnel in vehicles, including the driver, remain seated at attention."
Of course, you're not required to follow military regulations if your ceremony is non-military, but they're generally good guidance.
Salutes are sometimes rendered from moving vehicles during parades, when the vehicle passes the reviewing stand. However, the national anthem is not a march (it's actually in waltz time) and is not played during parades.
I hope this helps.
Peter Ansoff