Final answer:
Red-green color blindness in humans is a sex-linked trait that affects the ability to distinguish between red and green colors, and is more common in males than females.
Step-by-step explanation:
Red-green color blindness in humans is an example of a sex-linked trait. It is caused by a genetic mutation on the X chromosome, which is why it is more common in males than females. The condition affects the ability to distinguish between red and green colors, and instead, those colors may be perceived as shades of brown.