Congrats on your upgrade! Color grade has nothing to do with sparkle and clarity grade can in lower clarity grades or specific inclusions (type, size and location or the dreaded note on a lab report stating that clarity is based on clouds or graining not shown). Color sensitivity is variable amongst individuals. Some people can detect warmth in an H graded stone (assuming graded by a reputable lab like GIA), others cannot. Color is also more noticeable in a larger diamond vs. a smaller one of the same color grade and in certain shapes (elongated shapes like ovals and pears, for example). Strong or very strong fluorescence can in some cases cause a milky appearance, but it can also make lower colored diamonds appear more white in some cases. Medium or lower fluorescence (as graded by GIA) is generally safe except in rare cases (D-E color or with a lot of clouds or graining, which can enhance its effects). So color and clarity really depend on which lab graded the diamond and it’s the size and shape (and specific inclusions and their locations even in higher clarity grades). But as
@Swanky noted, it is cut quality (not to be confused with shape) that is the most important factor in determining a diamond’s sparkle. And while the highest cut graded assigned by a lab is a good place to start, GIA Ex Ex Ex for example, it is believed by true diamond enthusiasts that the lab’s parameters for cut grade is too broad (done so more diamonds can be sold at the premium of Ex Ex Ex) and there are tighter proportions within GIA’s Excellent cut grade that are most desirable and result in the best sparkle. You don’t mention what shapes you are considering, but I am speaking specifically of modern round brilliants (GIA doesn’t assign cut grades to fancy shapes, so for those even closer scrutiny is needed). I’d suggest you see some diamonds in person in the size and shape you are considering to check your sensitivity to color and the effects of fluorescence. Make sure they are all graded the same lab (ideally GIA, which is the most reputable now that AGS is no longer) and view them in normal, everyday lighting (not jewelry store lighting, which is designed to make even poor quality diamonds appear bright, white and sparkly). Also check out PriceScope dot com for loads on info on diamonds. The folks on the Rocky Talk forum there are diamond enthusiasts that will be happy to help you out. Good luck with your decision!
