A man with color blindness will se the Red color as:

The most common form of color blindness is red-green color blindness (protanopia/deuteranopia), where individuals have difficulty distinguishing between red and green colors. Many people with this condition perceive red as greenish or yellow-green, while seeing greens as more muted. This is because the cones in the retina responsible for detecting red or green wavelengths don't function properly.