The question requires us to specify in which part of the electromagnetic spectrum the wavelength given (450 nm) falls.
Considering the electromagnetic spectrum scheme presented in the image below, we can affirm that decreasing the wavelength means increasing the energy (the smallest wavelength values shown, for example, fall in the gama ray section, which is a very energetic wave). Also, we can see that the visible region of the spectrum occurs between 380 and 750 nm:
Therefore, the wavelength given (450 nm or 4.50 x 10^-7 m) falls within the visible region of the spectrum and it refers to the blue color.
