You're right, if the wagon is all white.
But You can go to two-tone paint and paint the roof according to interior colors - I did it this way, to avoid the frigidaire-ambulance etc- look..
I love that! Here in Georgia though, we like the ambulance look. I call it the polar cap treatment. Sure keeps them cooler in the summer. I might paint the top white on mine.
Maybe something kind of like this. Maybe some white pinstripes to help add some flair.