My costume was black, white and silver. As you can see my necklace was mostly yellows, golds and browns.
I am not sure when or why I bought the necklace but I have never really liked it so the idea came to me to paint it. I tried some fabric paint first which was quite unsuccessful and then it occurred to me that fingernail polish might work.
Here is the result of that experiment using black and silver fingernail polish. It may chip of course and I missed a few spots but all in all I was quite happy with the result.