As in title…
None in the New Orleans area, nor in the Jackson, MS area, are painted that way. Can’t speak for elsewhere.
Can’t think of a single Japanese restaurant I’ve every been to that had orange walls. Most of the ones I’ve been to feature light, natural wood, like pine or bamboo sort of colors.
I don’t know about proper Japanese restaurants, but I’ve been to a few orange-walled sushimi places in British Columbia, Washington, and California. Ranging from sort of reddish/burnt-orange to bright kindergarten orange.
I don’t think there’s a “why” for it.
On the other hand, I suspect that a lot of take-away curry shops are that particular shade of dark yellow to minimize the appearance of grease and cumin stains. 
At Chinese New Year, they give an offering of oranges and lettuce to the dancing lion to bring prosperity. The oranges symbolize gold and the lettuce symbolizes money. Maybe the orange color is meant to bring prosperity to the restaurant.
The only Japanese ‘restaurants’ I’ve seen with walls like you describe are of the Yoshinoya chain (fast food). Regular Japanese restaurants tend to be just a tad classier…
Well, by golly. Courtesy of the Hiroshima Gas Company:
I don’t know if that’s a widespread cultural convention or not, though. It appears that the Hiroshima Gas Company’s Colour Producer studied under some Western theorists, as well.
A bit hippy-dippy, but maybe…?
Maybe a little geographic survey would be enlightening. Where are you, approximately, PecanSandy?
I’ve definitely noticed this tendency (in sushi places) – can’t say that I go to a lot of Japanese restaurants, so I dunno about them, but sushi joints, yeah. Stands out because I really have low tolerance for orange.
Could this be something that’s more common on the Pacific coast?
What about Japan?
I’m in the Philadelphia PA area.
3 of the sushi places in my area are privately owned, high quality restaurants (very good food, service, and decor), and all 3 of them have bright orange walls.
There is a psychology to food and appetite. One link is
Red is touted to whet one’s appetite. Most fast food places’ tables are yellow as their studies found that to do it. Orange is in between.
Here’s another goggled for “appetite and color”