The original McDonald's arches designed by Stanley Clark Meston were yellow.
Meston created the distinctive restaurant architecture in the 1950s, when McDonald's was developing a recognizable roadside identity. The large yellow arches were visible from a distance and helped motorists identify the restaurants before standardized highway signage became as extensive as it is today.
Yellow also contrasted strongly with the surrounding roads, buildings, and sky. That visibility made the arches effective as both architecture and advertising, even before the company treated the shape as a formal logo.
The arches later became known as the Golden Arches, although the exact shades used in signs, print, packaging, and digital media have varied. Their original yellow color is the key historical fact behind the familiar name.