Which set, for which character, and for which game? I have lots of sets of dice as well as unique individual die, and I try to match them to the characters and/or games I'm playing. For Traveller T20, for example, I have some spacy, futuristic sets of dice.
For my home campaign, I have sets to represent both of my characters: Mostly black, grey and red for my fighter/rogue, and colorful Mardi Gras swirls for my bard.
For playing RPGA, I have a couple of sets I use that are primarily red, although there is one green d20 and a white d20 with black numbers in the bag as well. And a matched set of blue d6s for my rogues' sneak attack damage.
For DMing RPGA, I use my colorful DM Dice o' Death that came in the d20 Basic Edition box set. Each die is a different, bright color.