What color temperature is well suited for diamonds and jewelry in general?

The best color temperature that is well suited for diamonds would have to be in the range of 6000-6500K or Kelvin color temperature. 6000K is your neutral white daylight color, anything under will start to turn to the yellow category and anything above will turn to the blue category. A bluer cast over diamonds will sparkle them fantastically, but they would give a lot more of an unnatural tone to the jewelry. Therefore getting the best possible neutral daylight look will not only sparkle your jewelry but bring out the scintillation and clearly define the Cut, Clarity and Color of your diamonds as well as all your other jewelry whether it be fine jewelry, fashion jewelry or costume jewelry.