Answer:
The sweatshirt is blue because the pigment in the cloth reflects the wavelength of light that is visible to the human eye as the color blue.
Explanation:
Details:
The way we perceive colors is dictated by what wavelength of light they don't absorb (or the only wavelength that 'bounces off' of a certain pigment). I won't get into why pigments reflect certain colors and absorb others, because it isn't important to the question.
The main thing is, the wavelength that isn't absorbed by the sweatshirt is the wavelength that we perceive as blue, so that is what color the sweatshirt is to our eyes.
Hope this helps!
