I didn’t even realize they had ever been in color…

Infrared and X-ray spectroscopy can help researchers understand what the paints are made of, and how they looked all that time ago. Spectroscopy relies on the fact that atoms are picky when it comes to what kind of incoming energy they absorb. Certain materials will only accept certain wavelengths of light. Everything else they reflect. Spectroscopes send out a variety of wavelengths, like scouts into a foreign land. Inevitably, a few of these scouts do not come back. By noting which wavelengths are absorbed, scientists can determine what materials the substance is made of. Infrared helps determine organic compounds. X-rays, because of their higher energy level, don’t stop for anything less than the heavier elements, like rocks and minerals. Together, researchers can determine approximately what color a millennia-old statue was painted.

i09: Ultraviolet light reveals how ancient Greek statues really looked

… but I think I prefer them without.