For example, if the vehicle were backed down a beach incline, the white roof top and white side canopies would dominate the view... a passerby would reasonably perceive "white" as the color.
But one would presume that fishermen would be at sea level, not looking down an incline.
Yes, the fishermen presumably would be at water level... but visualize the parked vehicle pointing uphill on an inclined beach... from a boat in the water, you would see more of the white top and white side/rear canopies of the vehicle... factor in the time of day, as Palladin suggested... and you get reasonable witness accounts of a "white Suzuki" on the beach in the early AM.