How does the construction of an LED affect its color output?

The construction of an LED significantly impacts its color output, which is primarily determined by the materials used to create the semiconductor junction within the LED. Different semiconductor materials have distinct energy band gaps, which dictate the color of light emitted when electrons recombine with holes in the material.

When an LED is energized, the recombination of electrons and holes releases energy in the form of light. The wavelength (and thus color) of that light corresponds to the energy of the photons emitted, which varies based on the semiconductor materials employed in the LED's construction. For example, gallium nitride (GaN) can produce blue light, while gallium phosphide (GaP) can produce green light. Therefore, the choice of materials is crucial in determining the specific color that an LED emits, making it the correct answer to the question.

Other factors such as size and current can influence brightness and efficiency of the LED, but they do not fundamentally change the color output determined by the materials.