The human eye can only see white visible light and it contains all the colors of the rainbow, from red to violet.
Explanation:
But visable light comes in many "colors" such as radio, infrared, ultraviolet, X-ray, and gamma-ray that are invisible to the naked eye.The reason that the human eye can see the spectrum is because those specific wavelengths stimulate the retina in the human eye.
The gold leaf (not foil) is to give a sculpture or a painting appeal. Without it, it would discolour quicker.The gold leaf can be easily removed if needed to be.