Why does a red apple appear to be the color red? Would the red apple appear to be the color red if blue light illuminated the apple?

In white light, a red apple absorbs all the colors (including green) of the spectrum except red, which it reflects. When the green light shines on a red apple, the red apple absorbs the green light. Since there is no red light shining on the apple, there is no red light to reflect, so the apple appears black.

Genetics

Explanation:

The color of the apple arises from the level of expression of certain genes in your skin or peel

Enzymes work together to convert certain molecules into pigments called anthocyanins, the same class of substances that give purple sweet potatoes, grapes and plums their color. The levels of these enzymes are controlled by a transcription factor, a protein that regulates the expression of a gene called MYB10, so that the more MYB10 there is, the redder the shell will be in general.

If a red apple is illuminated with a blue light, it probably looks like a violet color. This is because the combination of colors (both in paints, red and blue, or in this case the superposition of tones) results in a bruised tone.