Extremely subtle color differences can be very important to determine rarity of a engagement rings, but are never a critical factor in beauty.
The first step in manufacturing a fancy diamonds is to give it to a cleaver or sawyer. They both, essentially, perform the same task: That is to cut--or cleave--the GIA Certified Diamonds in two pieces in order to bring out the best profile that will determine the end product of the stone.
Most titanium ring, although appearing colourless, actually have slight tones of yellow or brown. As these tones become more easily apparent, the rarity and the value decrease.