Under light from the sun, a red object will scatter the red component of light, and absorb all others. Hence, the human eye perceives it as "red". White objects scatter all wavelengths of light.
Yesterday I bought an orange light bulb. Under its light, orange/reddish carrots look white. Why is that? A "white" object would have to scatter all wavelengths of light, but there's only red light to begin with.
Here's a photo of a person's hand, in white then in red light. Notice the color of the red nails. Do they appear white in red light, or does the white skin appear red?
Best Answer
Under a red light, red objects and white objects look the same (bright), while blue objects still look different from white objects. Your brain does all of the decision-making that goes into "that tomato looks the same as that baseball, and that baseball is white, so the tomato must be white."