Chameleon diamonds are one of the most interesting and unusual segments of the rare colored diamond market as they are the only diamond that changes color. These dominant green stones have become popular in Asia as well as with sophisticated collectors and dealers who are attracted to the rarity of the color green along with the unique color change. We have started to see some strong selective sales of chameleons at the auction level and these pieces make very attractive rings and pendants.
Chameleon diamonds exhibit a range of hues and tones from light to dark olive (stable color phase) through light to medium yellow (unstable color phase). After 24-48 hours in darkness, exposure to light slowly changes the color of a chameleon diamond from the unstable yellow phase back to the stable olive phase. This is observed as an infinitely repeatable process.
This transition is illustrated in the second and third image here.
Chameleon Diamond Intensity & Hue