I use a variety of colored rings. They can make a piece feel playful or just simply zest it up. They are either anodized (which is, putting it simply, being zapped in a solution with a particular voltage for the desired color - awesome!) or they are enameled. (Anodized aluminum is a little different in that it is zapped first to prep surface and then dyed.)
Anodized Aluminum [AA]: ~ 98% aluminum, ~ 2% magnesium. Anodized aluminum is probably the most "delicate" of the colored rings. It still holds up well with use, I would just recommend setting it on the table at the end of the day instead of tossing; the color can chip and scratch. The color will change over time, which is determined by your personal body chemistry. DO NOT use a polishing cloth on anodized aluminum as it will encourage the colors to change faster.
Enameled Copper: copper rings coated with a polyurethane and nylon blend.
Anodized Niobium: pure niobium. Oils from your skin may change the color over time.
Anodized Titanium: 90% titanium, 6% aluminum, 4% vanadium. These are incredibly strong and lightweight.
Allergy: See Aluminum and Copper for anodized aluminum and enameled copper. Niobium and titanium are hypoallergenic and are great options for people who have had reactions to other metals.
To clean: Soap and water works well for the colored rings. If your jewelry has a combination of metals, know that the colored rings are safe in the cleaning instructions for copper based metals.