This study intends to suggest methods to improve public sign colors for the visually impared people at subway stations. We investigated the color universal design of public signs at subway stations in Seoul, Tokyo, and Yokohama to explore how to advance the public sign design of Korea. To achieve this goal, we conducted a critical literature review about color universal design and then identified its characteristics by comparing the current color universal design in Korea and Japan. We carried out color sampling and analysis in both countries and described the issues and challenges. Compared with the sign colors in Korea, those in Japan showed higher luminosity contrast, thereby supporting the visually impaired people in a more adequate way. Finally, we proposed guidelines for designing of public sign color, expecting that visually impaired people will be better assisted everywhere in the world.