Most of the time, diamonds will exhibit a blue color fluorescence under UV light. Although there are constant debates and no real guideline on the effects of fluorescence on the color of the diamond, some studies suggest that blue fluorescence can make yellow color stone appear whiter while strong fluorescent could cause pure colorless diamond to appear milky and oily in regular light.

 Hence as a general rule,

For color grades H-I-J-K: Choose fluorescence medium or faint blue and it will look 2 grades whiter.

For color grades better than G: no fluorescent or faint one is advisable.

 Do note that there are instances whereby strong fluorescence in lower color grade diamond exhibit milky or hazy characteristics. Hence, strong fluorescence is usually discouraged.