loose diamond experts would never attempt to verify a diamonds color in a setting, and would insist on a certified color comparison before attempting to make a fair evaluation, confirming how difficult differences in color grades are to see.
gold engagement ring have traditionally been graded using the 4 C’s. Carat weight is simply the weight of fancy diamonds. Color and clarity are important when determining the rarity of fancy diamonds. Cut is the C that helps determine the Light Performance of fancy diamonds.
While the weight of a diamond earrings is important, it doesnt necessarily provide the "perceived size" of a fancy diamonds. A shallow cut diamond will have a greater diameter, and will therefore look larger.