Ray St. Clair first learned he saw things differently when he was about nine years old and walking down Congress Street in downtown Tucson with his mother. "Look at the gray car," he said to her.

The most common types of color blindness, or color vision deficiency, are genetic. However, other types may develop due to injuries, eye diseases, health problems, and side effects of treatment.

Dr. Mark Lindsay was 5 years old when he first learned that tree trunks were brown. "Up until that point, I believed leaves and trunks were all green. Just lighter and darker shades," Mark said. Mark ...

Color blindness, or color deficiency, causes difficulty telling different colors apart and may affect the shades and brightness of colors. Color deficiency can occur in females but is much less common ...

An estimated 300 million people worldwide are color-blind. This typically means they can't distinguish certain shades of color, they struggle to tell how bright colors are or, more rarely, they can't ...