Get some modern darker colors (gray/black/blue), do the trim in a white or light gray, and make it pop with bright neon or red hoses/vacuums. Whether its in a good or bad neighborhood everyone appreciates a modern looking structure. When I was remodeling, cant tell you how many people stopped by just after I had mine repainted. In no way am I a car wash expert, but I do understand the psychology associated with visual appeal. A drastic change in the colors, will attract the attention of those who drive by every day.
This fall, I'm going to upgrade the look of mine with some sheets of Corten steel, on the front/sides, which should compliment my stainless steel lettering.