You could buy a nice looking ring for hundreds — or even many thousands — of dollars, but if you really want to stand out, then this laser-cut black acrylic finger ornament from Charlyn Gonda could be just the thing. When turned off, it simply looks like a black hexagon on your finger, but when switched on, an array of seven RGBW LEDs shine though for a somewhat surprising effect!
The trick here is a material called Chemcast Black LED Acrylic that was purchased from TAP Plastics, though it might be available elsewhere. It looks nice and black when no light is shining, but diffuses the LEDs behind it when illuminated. The LEDs here are provided by an Adafruit NeoPixel Jewel, which slides nicely into its hexagonal enclosure. Which light shines, and what color, is controlled by an external Adafruit Gemma M0, wired through a hole in the base of the ring. Power is provided by a 160mAh LiPo battery, and as seen in this tweet she’s been able to hide the supporting electronics in what you might call a “power bracelet.”
Code for the build is provided on the project write-up, and vector files are found on Thingiverse if you’d like to make your own. If manufacturing your own ring isn't in the cards, Gonda hints that these may be available for sale later, so be sure to follow her on the various ways mentioned on her site to see when it’s available!