Stanford Medicine Jan 24 2026 Recognizing the sight of blood in urine, the most common first sign of bladder cancer, is often the impetus that leads people to a diagnosis. But for those with colorblindness, who usually have difficulty seeing red, that warning sign is more likely to go down the toilet unnoticed. Now a study by Stanford Medicine researchers and collaborators has found that missing this early sign can have serious health consequences. In an analysis of health records, they