Hmm.

I have a silver ring with a black stone that I don't wear. I can give it to you. Although my belongings exude hopelessness and emptiness, so it probably won't be suitable for your purposes.

kek. Once, some Indian friends gave me a lecture about the meaning of the color of the stone for the owner of the ring from the point of view of Indian tradition. So, a black stone (from the point of view of Indian tradition, of course) evokes submission to fate and is very likely to cause apathy (unless the person's horoscope has some strong celestial bodies... blah-blah-blah... I got lost in the details at this point).
The most popular colors for them are blue, green, white, and yellow. They suit everyone.